Yeah.... There is going to be no short cuts on that one. You are going to have to buy a universal remote (one with a large IR library). I would suggest a cheap One-For-All remote to start.
Find a comfy spot to sit for an hour and go thru every TV code on the remote. Hopefully one or more of the codes in the database will work. There is a small chance however, that this might not work either.

Here is a good one to try:
[Link: amazon.com]