titan mauler, gravity bow., and orc hornbow come to mind.

Raw ring of spell storing can get you 5 gravity bows (50k-gp), but considering the actual damage out put if increasing size. It's closer to flaming weapon enchant. Most of the tables I've played at allowed archers to buy gravity enchants as a 2 (20k-gp). Ask your DM if they are open to this.

If no third party content, go tiefling with the oversized limbs to reduce the attack penalty, if third party is allowed, go with any of the powerful build races (I like half Giants).

If GM agrees to all of this, and is agreeable you might end up with a medium creature firing gargantuan ammunition from huge bows. I don't see why a GM would say no cuz mathematically it's an inferior build option. It's almost purely RP, and unless your fighting mostly outside the size of the weapon will be a hindrance itself.

A long bow is 5ft at med, 10ft at large, and 20ft at huge.
A short bow is 3ft at med, 6ft at large, and 12ft at huge.
Doors, halls, and most places will be an issue