Most of the control heads for the Kenwood '700 series of radios are interchangeable (but not all of them!). Finding an exact replacement is going to be problematic, sort of, and will depend to a great extent on how much you can afford, what it's worth to you. If your 'radio' is working correctly and you only need a control head, maybe the cheapest option would be to find a used '707 with a 'shot' 'radio' and a working control head. (Yeah, right!) Or, chew on that 'bullet' a little and just replace the whole thing with a newer radio?
Good luck.
- 'Doc
(Nothing new here, and not really much specific help, huh? Sorry...)