Go to any good autoparts store that will let you look at the big filter catalog from WIX, Baldwin, or any of the big industrial filter makers. (And probably WIX, NAPA, and Baldwin are the only ones.)
Look for a filter element that (1) fits the thread, gasket face, length, and diameter you have to work with, and (2) is listed either for hydraulic use or combination engine oil & hydraulic use. These will filter ATF better than a filter listed just for engine oil.