You can have Donna make one for you. But that would be after you come to Andorra. To come with one already in hand, the HRs allow you to spend XP instead (as an abstract).
If the character has access to Expensive armaments.
Superior (+1 Attack) = 2xp
Supreme (+1 Attack & +1 Damage) = 4xp
Excellent (+2 Attack & +2 Damage) = 12xp
Exceptional (+3 Attack & +3 Damage) = 24xp
The formula is qp (or xp) equal to twice the pyramid value of each bonus provided.
Armaments
Items of Quallity
Any better than +3/+3 has to be gained in play. Siveroak's character Donna can make a weapon that is as good as +5/+5. Maybe.