There are many, many of them out there already in use by reenactors etc. The reproductions are readily available for sale with just about any unit etc. you may care to have. Originals are obviously very rare and costly, most of what you see out there on eBay and such are fakes, but occasionally at better militaria shows one finds good originals for sale (not cheap!).
The fakes and legitimate reenactor reproductions are most often 'lifted' from original impressions on documents and cleaned up and reproduced--some folks are quite good at this and have done hundreds of different ones.
By the way, the reproductions very often make much better images than the originals did because they are softer plastic instead of hard rubber or metal.
If you are looking for particular ones, you might contact one of the makers.