NOTE: If you think you might mess it up somehow, you can use a box cutter it similar to scrape some larger chunks of polymer from the grooves. Then if you have to (or have to pay someone else to) attempt fixing it, you'll already have the right polymer on hand for welding. It seems like nothing quite matches Glock polymer but Glock polymer! Lol.
Take Care,
Mike
AR grips from lower parts kits blend very well. That was always my go to plastic when I was doing grip reductions.