If buy in packs of 5 expect to pay near 90 cents each. You can get a 100 to 200 packs off
ebay for around 60 cents each.
Some come up in auctions (like current Rasdale auction) but not sure what you are really getting (quantity/size). For US plate blocks the sizes would usually be 2, 3, or 4 pocket depending if you want plates oriented correctly.