You really can't find a mouse 20cm long but some good mice for cheap include Rival 310, Logitech g203 and the Razer Deathadder Essential. Find which one looks the best and meets your standards. I recommend going to a computer store which allow you to test some peripherals. Find a cheap mousepad which meets your standards as well. It doesn't matter if you don't get a RGB 100$ mousepad, any will do as long as its the right sizeI use mostly palm grip
About the pad: I remember I had a mat before, and whenever I lift the mouse and put it back on the pad it just has bounce back movements.. like it makes it move unintentionally. I was never sure it was the pad or the mouse I was using, but I just used on my table and it worked well. If you have a good pad that won't do it I'll try it (Not too expensive)
I buy from Amazon
I have one that's close, Asus ROG Spatha, I think it was designed for football players and wrestlers LOL It was the only mouse I could find that had the button layout I liked though, and I happened to look when it was on sale for a relatively cheap price for it.my hand is 20 cm length it's not that I'm looking for a 20 cm mousethat would be a huge mouse I think. I will try one of the 3 you mentioned!