What kind of sheath were you looking for?
Would you be happy with 0.060" thick kydex?
What kind of carry system did you want?
Your best bet would be to try Britishblades.com, however the three people that came to my mind have been mentioned and it sounds like they aren't really available right now.
I can do kydex, but I have a couple of knife commisions sitting and eyeing me accusingly from the work bench, so I couldn't guarantee exactly when it would be done. I also don't know what the going rate is in the UK for kydex work. In the US a Grunt sheath is probably between $25 and $50, against which you have the fact that many people here sell themselves cheap, but the material and fittings have to be imported. I would reckon on one being about £20 here, but that is just a guess.
Have a look on BB, put down some more specifics, you never know, someone might jump forward