My thought would be to buy a pack of glow sticks and then poke a hole in the side with a safty pin(Be careful the glow stuff is poison and when you poke the holle in it it will pray out a little) wipe the glow stick stuff all overr the stringg let it sit 4 about 2 hours vand then reapply the glow stuff.
I did this with my YYF Starlight and let5 me tell you it looks pretty awesome! ;D
If i remember right theres a way to mix phosferus and bleach and somethin else and it makes a glow in the dark dye… do some googling and you’ll find something