GE filter, flow washer transmissions
Yes, your best hope is as Melvin suggested is just finding a good one. You might also find a low mileage machine where it's not leaking yet.
Back in the day when these were popular we just always bought remanufactured ones from GE but it's been many years since they were available, I've saved a few good ones for the couple machines we have in the museum, personally I wouldn't bother using a filter, flow washer as a daily driver, unless you're willing to put in the work of keeping it running.
I had a new in the box all metal transmission that we put in a 1966 unit a couple months ago that I had bought from a parts dealer where it just sat forever. That was kind of fun.
John