I found these being sold (for P250 I think each) at 168 Mall over in Divisoria last December. There were also wallets in American dollar currencies and some in Dinar and Japanese Yen I think.
Imagine putting your american eagle silver dollar in something so quirky. Nice gift idea for friends who like conversation starters, eh?
I only saw one stall selling these and it's located at the ground floor of the old 168 building. Just keep an eye out, it's in one of the first two aisles from the left.