Every now and then I see them come up on egun.de. I picked up a Zeiss that was actually marked "Johann Springer Erben". It's currently being fitted to my M1910...

FWIW, optics are controlled under Department of State guidelines as not for export. Seems your average DoS/Customs guy can't tell the difference between a 80 year old scope and a new, thermal starlight scope. So they just restrict them all.