The only ones I can think of are the Magical Qualities Extra Fatigue or Grant: Extra Fatigue. Any others out there?
The reason I asked is that Hermetic Inclination by (Form) fatigues the artist while crafting, and that means for most mortals it is hard capped, going above level 49 renders you unconscious for the duration, which means you never finish)
Let's ignore for the moment the unlikelihood of a Maestro getting a lab total that high, it is possible, if barely.
A Familiar?
I think they'd be hard capped at an even lower level. Given that wound penalties between -3 to -5 prevent lab work and craft work, being Fatigued to -3 to -5 should also prevent craft work/art.
I would not equate wound penatlies with fatigue. First, the subheading cover the penalties for wounds that you reference is Activities while Injured (italics mine).
You could do something more evocative, in that the artist constantly works himself to a frenzy, passing out while working, and is unable to do anything but work on the artwork. Might do a wound check at the end of such a season to determine whether he's harmed himself working too hard. Optionally, the artist might willing take a wound, similar how Hermetic magi can Life Boost and soak damage for additional penetration, if necessary.
But, one mus task, what effects are you intended to impart that require such a large investment?
How would a familiar give me a fatigue level, assuming I had access to one?
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As a Maestro, it would be a legendary one of course! Unfortunately a lab total of 50ish is really nothing special in hermetic terms. Still the higher he can go, the niftier the effect might be.
Better answer - nothing specific planned, just looking towards the future when his Terram score hits 20ish.
You kinda misattributed the quotation there... 
Be born Large?
Large doesn't grant an extra fatigue level. It increases the intervals for the different wound levels.
quote fixed, thanks.
Large adds makes each fatigue level wider, but you don't get any more of them. Similarly, all the related virtues I have found either do the same or add conditional modifiers.
I think the closest I've been able to come so far is macguyvering the virtue Ritual Power from ROPM to grant another magical quality, then using Mastery levels to reduce the cost of use. I think this would work, but would be prohibitively expensive in terms of virtues.
They're not the same thing, to be sure, but being at long term Fatigue levels of Tired (-3) and Dazed (-5) are people who are basically half-conscious. It seems a bit odd that someone with 3 light wounds is forbidden lab/craft work, while someone who is basically falling over from exhaustion for an entire season can blithely soldier on. And it gets even stranger, given how the Life-Linked Art allows the character to take wounds to improve Aesthetic Quality, even though Medium and Heavy Wounds would preclude working by RAW.
Personally, I'd prefer both effects (Hermetic Inclination and Life-Linked Art) to take effect after the piece is done, and the Fatigue for Hermetic Inclination lasting as long as it took to create the piece.
It is pretty easy to recover from a light wound in a week. And so that would only be a distraction that might not even impact the lab total.
But, I tend to think it does work better to place the penalties after the piece is done, but something needs to happen during the creation process, too.
Extra aging rolls per season spent creating?
Bob
A familiar can share fatigue, right? Send the fatigue to the familiar, it rests and recovers, and you keep going. If the fatigue is coming slow enough, you should be able to work indefinitely, yes? And I would swear there are spells that allow you to give fatigue to others, as well......
Not unless it has a power that enables it to do so. Familiar powers don't normally allow sharing fatigue.
Ah, right, Spirit Familiars can do that, my bad.
Or get a folk-witch to brew you an unfeasibly large number of fatigue restoring potions.
Bob
Do large animals potentially have extra fatigue levels? (Health levels, yes - I don't recall about fatigue, though.) If they do, my thought is "shapeshift".
Other than that, yeah: Integrate and/or know a friendly hedge witch.
No, they change their wound levels, which only affects fatigue in the event of non-lethal combat (which does fatigue).
You must take Qualities that add additional fatigue to have additional fatigue.
Shapeshifting is potentially still an answer, though - some animals do have extra fatigue levels, it's just not particularly linked to size (boars have +3, bears have +2).
Changing into a boar could make artistry difficult, mind.
ReCo20 The Gift of Vigor on a stick?
Then have a few people zap you every day.