Short of buying lots of box sets to complete the series, or ripping open the boxes in a superstore and stealing them (neither is recommended or endorsed by us!!), your best bet for completing the collection is to search for Monopoly tokens on eBay.
We've done all the hard work (don't pity us, please): set up the widget below for you to begin your search.
See something you like? Great, simply click to be taken directly to the auction item.
It's also worth having a look on Amazon, as some people sell the rare Gold Tokens on there.