Dirt bucket? Picked up an old Vassar dirt bucket. ~200# empty. It has a dump feature. Might be too light for your needs. Multifunctional. Back end bucket, hauling firewood, ballast.
BX is a small tractor. Don't plan to push it to the limits. Right now just have the box scraper attached for ballast. ~300# IIRC. Seems to be good enough for balancing the grapple claw. But doubt if I'm exceeding 300# loads.
When pricing new of what looks like identical design they listed ~$450 + tax + freight fees. Used they should be less than $100.