Nobody specific, these things are ancient. However, any good electronics technician can likely repair it. It might be as simple as replacing all the capacitors and resoldering any bad solder joints that have developed.
By the way, this receiver isn't really good for anything anymore because it's obsolete, and there's no analog signals left. What do you need it for? Are you just using it to move your dish? If so, this would be better for you and likely cheaper than finding and paying somebody to repair the Supra: