tyre clamp (rim lock, security bolt, etc.)

[dougxr]

Hello all,
First of all let me apologise if you've read this before - I've posted the same question in lots of places, so far without any luck.
I'm trying to find a tyre clamp (or rim lock, etc.) to fit to the rear wheel of my F650GS Dakar. The wheel is 3.00x17 and the widest clamp I've found so far is to fit a 2.50 wheel.
I realise I might be better off changing the whole wheel for something like a 2.50x18 but I'm trying to avoid that expense for the time being.
Does anyone have any suggestions where I might find a suitable clamp? I was hoping that I'd find one off one of the larger GSes but no luck as yet. I'm in the UK but if one can be found elsewhere then I'd definitely consider shipping it here.
Any suggestions or advice would be appreciated,
Doug.