How to buy polyhedra?

Excuse me, could you please elaborate on the process of purchasing polyhedra? I'm quite intrigued by the concept but am unsure of the specific steps involved. Is there a dedicated platform or exchange where one can acquire them? Are there any prerequisites or regulations that need to be fulfilled before making a purchase? Additionally, what factors should I consider when deciding on the quantity and type of polyhedra to invest in? I'd appreciate any guidance you could provide on navigating this process.