Purchased this processor with the amplifier in 2000. Original owner. No luck finding a remote, and unfortunately the processor can't be manipulated with it.

Any ideas?

Well, the IR signals are well known.  See for example this thread and the link to Pronto Hex.  That thread also tells how to manually program e.g. a Comcast cable remote (or any higher end remote made by UEI, like OneForAll) to send the necessary commands.  If you get a remote made in the last 10 years or so, it will need 5 digit EFCs.  Prepend 2 zeros to the EFCs listed the thread.

Do make sure to use setup code Video 0582  (20582 on remotes like the Comcast).