Here's one that looks quite good, it's an eBay jobby but UK like you wanted.

Reading the description he seems to know what he's doing re 7mm shank (rigidity).

I'm going to order one and give it a go, though he's got video on YouTube showing them at work, there's a video in the listing too but you'll need to view it on a desktop pc or lappy.

eBay Link:
CNC Drag engraving tool for router or plotter. Spring loaded.

http://m.ebay.co.uk/itm/152025476127

.Me