As tempting as it is to go to R.S. for that quick-turn / immediate gratification, you can do a lot better ordering them from the plethora of vendors on the Web. Sometimes, if there is an Industrial Electronics Surplus / Recycle store in your vicinity, you can get some fantastic bargains on both new and pulled fans. If you go browsing at one, remember to take a small gell-cell 12V battery and a couple of alligator clip leads with you to test the used ones before you spend your money.
73, Hoot