spring, fomerly crow electro make controllers for several of the main suppliers.
I bought one from them direct as they are not far from me. I have their new 3 button digital type (v9 or something like that) that replaced my original analogue dial one that incidentally still works faultlessly after 5 years. Having read so many posts on here regarding problems with varistreams I would say the ones spring make are the best (maybe biased as I have used no others) having met Phil and seen where they are made I have faith in the quality control, they are very robust and well designed to do what they are meant to.
Simon