Where can I find this coin?

These were sold by Canada Post as Millennium keepsake sets in 2000. The medallion has a face value of 25 cents but it is not a legal tender coin and has no monetary value. You can find single coins and sets with stamps, as issued, by looking on eBay from time to time. Don't jump at the first you see. Watch for a while to see what selling prices are, not asking prices. Some folks ask ridiculous amounts for their stuff, and sometimes, they get it, from people who are impatient or don't know values.