Always on the look out for a solution to this myself.
Surprised no-ones mentioned AV panels on the wall (Wired not remote one mentioned above) :( Solves problems of things going missing! And gives shiny coloured lights!
We found online a projector remote holder that screws to the wall and has a mirror at 45 degrees in the top. Teachers can get to the buttons. The remote is secured in via padlock. Trouble is they were 60-70 pounds.
I had a word with our DT dept who now make them for us out of plastic.
They do the job well. Haven't got round all room at the moment. So still buying a few which we charge to the departments.
Saved us loads
We started using something similar to the KPMS recoiler. Ours came from Loxit.com and cost less than £10. They don't seem to show on the website but when I was looking called them to see what they could suggest. That said an ex-collegue came up with something costing £4 which I will post here when I know where to get them from. A teather is not very secure but it does stop them being 'borrowed' by staff.