Fox green 10wt was pretty cheap at Evans at the last time I looked.
I’ve just been through the same thing as you anyway (as Evans won’t ship fluid to France). See the two links below – Fox green 10wt is actually pretty heavy, comparable to most other 15wt fluids. Suitable alternatives look to be Silkolene Pro RSF 10wt, Maxima Racing Fork Fluid 15wt, Motorex Racing Fork Oil 15wt, Rock Oil SVI 15wt, etc. The Rock Oil is cheap at Chain Reaction. I’ll be putting Motorex 15wt in mine this week as that was what I could get hold of easiest.
http://www.peterverdone.com/wiki/index.php?title=Suspension_Fluid
http://www.transmoto.com.au/fmx/products/7799233/