It would be a little bit more challenging with transgender men because the structures to support the testicle aren't present, but with work it could be done.

There's also the possibility of transplanting a uterus into a transgender woman...which again is a lot more complicated. Uterine transplants have been done for cisgender women with deformed or absent wombs, although typically they don't last the life of the recipient...uterine transplant recipients typically have the organ removed after pregnancy.

And yes, trans women might well be a potential source *except* for one thing: Most trans women who have bottom surgery have been on testosterone blockers for a while, which would reduce the quality. Having an orchidectomy without hormones first is, I believe, not great for one's health.