i'd try looking on ebay (however I just looked and there was nothing), or there's a wodent wheel look alike, the trixie wheel, which is available cheaper (although I've heard the quality is definitely less)
This is the cheaper 8" version
on ebay and
equine canine feline if youd rather buy from an actual shop.
Other than that the only place in the UK for ACTUAL wodent wheels is pet planet, and a girl waited for 3 months for hers, and it arrived without half of the pieces, so they don't seem that great with them. Users on here order from
transoniq. but obviously ordering internationally takes time.. and probably costs what you don't want to spend!