Someone on eBay UK is selling sets of 52mm UV filter, circular polarizer, and lens cap - for 99p! I always need 52mm skylights/UV and caps for the lenses I sell so I just bought a few which arrived today, and they appear to be exactly as described. Probably not up to the highest quality standards, but I'll be honest, I can't tell the difference at all, and they'll certainly keep the dust out well enough. Annoyingly they don't have any other size at anything like this price.
http://www.ebay.co.uk/itm/253149121163
Probably not worth it if you're outside the UK.