You can look on towerhobbies, they carry a novak fan that is iirc 25mm x 25mm, which should be the same size. You can also google it or look on ebay for a fan. Ebay's a great place to get those little things..
There was a guy selling replacement fans for Novaks over on RC Tech, that were nice fans at a cheap price. You could try looking him up to see if he has/can get one for the RX8. Just do a search for Novak fan in the for sale forum he should come up.