I'm more looking to replicate the waving effectI got a suggestion, but it depends if you want this effect only for the bow? and does it have to be a shader? if not, you could do it easly in the sprite editor:
here's a bow sprite I made for my own project:
In the sprite editor: do "Fade..." to the desired color, then save the sprite as png, open it in your image editor (I use paint.net) and add noise effect to it. Do this two times so you get the same bow, but with two different noise effect outcomes. Now, in GM's sprite editor, under animations, do "Morph..." and make the first sprite morph into the other one, then do "Add reverse", which turns out like this:
(made it into a gif for the sake of this example, so it looks kinda bad)
Now just change the opacity and draw this sprite on top of your bow sprite:
This is a rough example, sorry, but I hope it helps someone!