Congrats on your new G21. Glad you found something that works for you. Acessories? Well, here's what I would do with the G21 like I used to have. Full steel guide rod--like I do all of my Glocks past and present. On the G21, I needed an extended slide lock. I'd also look at a better set of sights than the factory, nite sights or otherwise. Good luck with it.