This uses the RC5 IR protocol, using device 28. Nearly any remote made by Universal Electronics can be programmed (by assigning 5 digit EFCs to each button) to control the C800.

I'm not sure which remotes are available to you. In the USA, Comcast or the Atlas remotes used by some cable companies have a setup code which can be adapted. Many OneForAll, Radio Shack 15-100/133/134/135, high end Vizio TV remotes, etc. can be modified.

If you simply wish to buy one, the RCA RCRP05B (Walgreens, Best Buy) or OneForAll URC-8820 (Sears) are less than $20.

Setup code Audio 1189 can be found in most of these remotes; several other setup codes are also useable.

To assign Volume Up:
First press the device mode button that you assigned Audio 1189 to (Probably Audio)
1) Press Setup (or Set or Magic) until 2 blinks
2) Enter 994
3) Press Setup briefly
4) Enter 21057
5) Press the Vol+ button
The remote should blink twice.

Here are some EFCs. If you decide to go this route, post back and I'll fill out the list of EFCs.

Vol + 21057
Vol - 21181
Mute 21177
Power On 20993
Power Off 21113