How to get 14.5x114 casings and ptrs41 en bloc clips?

I'm trying to get a collection going and I wanna get some 14.5x114 casings, living the Czech republic.
What should be the kind of price I would pay here for them? I will take even very poor quality casings, I'll be refurbishing them and adding fake bullets and primers so they look somewhat new.
I'm looking for originals, only source I found for these are people that don't know what they have and are selling them for cheap, however those are in limited numbers and only show up once every blue moon. Even then you have to fight for them in auctions which can get pricey.
Are there any other sources I can get to that would supply these? I also absolutely can't find the en bloc clips for the ptrs-41.
I don't think getting 6 rounds would be overshooting, 5 for the clip and one as a cool paperweight.