The other day I went and signed up at Listia.com, where you bid on items with credits and earn credits by auctioning items of your own, doing surveys, and watching videos.
Three of the auctions were for Monopoly money, 6 of each denomination,which I bid on.  I won 2 of the 3 listed items for a grand total of 12 of each denomination. This will come in handy as I'm starting to acquire supplies for my pnp games and will start assembling them within 2 months.