My attention has been drawn (as the libel lawyers say), by this discussion, to the remains of the commentary on Genesis by Theodore of Mopsuestia. These are not extensive, but are interesting.
Migne prints a bunch from the catena of Nicephorus in vol. 66, cols. 633-646. These are in Latin, not Greek, so I presume are from a publication of the catena which only consisted of an early modern Latin translation.
A bunch of fragments were also found in Syriac, and printed in Sachau, Theodori Mopsuesteni Fragmenta Syriaca (1869). Finally some more were printed in French, according to Quasten (I don’t have the details here).
The upshot is that most of what Theodore wrote on Genesis 1-3 is actually extant, if collected. It doesn’t sound like a great volume of data. Probably $500 would translate the lot.