Metal-geared servo recommendations

Can anyone recommend metal-geared servos that are easy to mod to continuous rotation?
I'm in the UK, and the devices need to be about the same size as the Futaba 3003 they will replace.
Weight/cost is not an issue, but size/modability is.

Not sure, but how about this? Dios — Kronos Robotics

Yes, I know how to modify a plastic-geared 3003 (I've done ten or more), what I'm looking for is a metal-geared equivalent, and how easy (or hard) it is to mod.