Heres a US source for mite paper:
Bug Kill and M'Lady No Bugs Insecticidal Shelf and Drawer Paper and Covering for Mite Control

Ebay might be worth a try too. Another alternative is to keep your cultures in a shallow tray of water. Keeping old cultures away and regularly making new cultures also helps keep mites under control. Unfortunately tho I have found despite your best efforts they are a continuing problem but you can take those measures to keep on top of them