Anything with a 128mm axle. Cheapy one, get a tensile off eBay, about £18 posted. If you want something a bit better, get a trialtech or a tryall. I would have thought it'll be a 68mm shell so it should just screw straight in. Bear in mind that the drive side is left hand thread, so don't try to force it in the normal threaded way, you'll knacker your frame up