Not an easy one, this and its sister version 7548 was used on diver's, these are both actively sought as donors. You may have better luck looking for a Pulsar Y513. Just for reference attached the service guide. Good luck.
Seiko 7546A - Technical Guide.pdf
I should have mentioned I will not get the stem from Europe, but am simply trying to get the right size. In fact, I may have one in my junk box. Yep, it's a Dollar watch and I'll do all that's necessary before investing money.