If you have some very fine soldering iron tips, you could solder on a small SPST switch and use a replacement resistor (or the original R8 resistor, if you can salvage it through desoldering.)
I’ve done similar mods before. A good soldering iron, steady hands, firm work holding, and a good magnifier absolutely help!
You’d basically hook it up as:
R8 pad A → thin wire → switch → resistor → thin wire → R8 pad B