OK, this is a very standard Comcast box so I don't understand why you haven't found a matching remote. These boxes all use the same codes:
Comcast RNG 110
Comcast RNG 150 PVR
Comcast DTA 100
If the built-in ones don't work then I have built Custom Remotes for all of them and they can be downloaded from the JP1 forum link in the thread I asked you to read.