I would suggest this sub-$8 remote control:

https://www.amazon.com/GE-4-Device-Universal-Designer-33709/dp/B01HSSAZX8/

I have half a dozen of these remotes in various rooms throughout my house, and I have yet to find a TV, new or old, that doesn't have a working code. The code sheet for this remote control model is here:

https://m.media-amazon.com/images/I/A1nTCna7TDL.pdf

There are 7 different codes listed for Symphonic televisions. I would be shocked if none of them worked. Someone else mentioned that Symphonic TVs were made by Funai, in which case there would be an additional 8 codes listed under that manufacturer.

Out of curiosity, how is the picture quality on this CRT television? The manual says it has an S-video input.