They aren't coins so a better place to discuss them would be the Exonumia forum. But there are none currently listed in Numsta to there might not be much help.
If you have some, please add them to Numista. https://en.numista.com/catalogue/contributions/pre_nouveau.php?type=exonumia
Don't worry about a perfect listing, just put in the information you have and the listings can be improved later.
For the total number available, here is a page that claims to have a complete set for 1991 to 2007: https://www.worthpoint.com/worthopedia/myth-magic-pewter-one-drout-coins-244555182
As for more purchases, just keep trying web searches and various eBay sites. (Probably other auction sites as well, but eBay is the only auction site I found with any listed in a quick search.)
Your profile says UK so here is a listing you might be interested in: https://www.ebay.co.uk/itm/275519573171
