Have you looked up the Hori Gem Pad 3? Good players recomended it to me, since Im also using the X controller (and failing a lot because of it too). Reviews are also good and the price is surprisingly cheap. I ordered one for myself, can't wait.
http://www.amazon.com/HORI-Xbox-360-Gem-Pad-EX/dp/B00EOI2I7W/ref=sr_1_sc_2?ie=UTF8&qid=1397099565&sr=8-2-spell&keywords=hori+360+gempad+ex
