Pearce Grip PG-26XL magazine grip extension (not pictured) that adds a pinky extension only, does not add additional rounds/capacity $5.
Safariland 074 Single Magazine Holder for Glock 20/21 but I also use it on the G29/30 shorter magazines two available only $18 each.
Tex Shoemaker 1911/Sig 220 & others Black Leather basketweave dual Magazine carrier. Fits up to a 2 1/2" belt, opening is 1 1/4" x 3/4" and 4 3/4" deep to curve on the closure. I used it with some Browning H.P. Magazines so this fits a bunch of different models. Excellent no scuffs condition only $35.
NDZ 11# recoil spring for G20 Gen1-3 $14 and NDZ 11# recoil spring for G20 Gen4 $18. Both are needed and work great for shooting 9mm from a conversion barrel in these 10mm Glocks. They will also fit into the Glock 40 and might work with others I am unaware of.
Will take pictures if needed that I assume will need to be sent by my email address to yours. Unless stated add 1st class shipping at cost to items listed, usually around $3.75 in a padded envelope.