OK, info I can find from about a year ago. I have not dealt with any of them so can't vouch for anything. First link is for a external crystal heater but that is generally for "already drifty" icoms....EDIT... I should have read the damn article first. I thought it was a slip-on type of oven deal. NOT SO, It's a rebuild of a EC icom to provide an oven inside the case. Nice.
MASTR II ICOM rebuild and temperature compensation
Another manufacturer but probably can't comp your elements. Can always ask though...
Cal Crystal is now Transko:
http://www.transko.com/
Cal Crystal Lab, Inc. / Comclok, Inc.
Transko Cal Crystal Comclok
3981 E. Miraloma Ave
Anaheim CA 92806
714-528-8000
714-528-8017 (fax)
Quartslab was mentioned as being in the UK in the list, ZZ has provided the link for them.
Shockingly enough, Bomar was / is still around. They said in a e-mail (a year ago again...) they were not doing temp comp service but they "might" in the near future. Worth a call or e-mail
1-800-526-3935
sales@bomarcrystal.com
If all else fails, I have 2 sets of Mastr II elements left crystalled in the UHF ham band. ICM crystals. A friend of mine did them in the late 90's. I cannot remember if he did anything to comp them but they performed well for eons. Gave away all of my GE stuff finally in February, These plus other elements in the commercial band all I have left.
Hope any of this info helps.
Dave