I hadn't thought about recasing, but that's an interesting suggestion. Might look into it if there aren't any other options, thanks.
I found this card, which I think would fit, and I've found some info that says it only uses less than 50W.
http://www.amazon.co.uk/Asus-Radeon-Graphics-Profile-Warranty/dp/B004XANP0U/ref=wl_it_dp_o_pdT1_nS_nC?ie=UTF8&colid=OGG172QZ6AVF&coliid=I1B0JYKNMD00XO
Might that be an option?