All over the place. GW don't support it any more, so eBay/resellers for GW figures, there are lot's of 3rd party "fantasy football" manufacturers and lots of people kitbash from GW WFB/40k models.
I'll try and get a list of 3rd party sites together in the next few days, but I think the cheapest option is Impact's Trollcast teams, resin-like:
http://www.impactminiatures.com/index.p ... fballteamsThey can be got direct in the UK from Tritex Games (
http://www.tritex-games.co.uk/), though the range is due to expand soon once they've finished shipping a Kickstarter that added 20 teams to their range.