Memento Coins?

So I’ve decided that each time I accumulate one full ETH, I want to buy a coin to represent it with my other metals I own (a little gold and silver).

Does anyone here have any links of good quality coins for display that won’t turn green after 7 days? I’ve seen some super cheap ones on Amazon but I really don’t mind buying real silver and have it as a double investment.

Thank you all.