I've been using this one for a while now. It's pretty good for what I need. It fits well with a bit of space but doesn't move around or anything like that. It's not the greatest quality, but it has held up well so far and it has a pen loop inside to hold your pen.

Edit: forgot link https://www.amazon.com/dp/B016VZYA5I/ref=cm_sw_r_cp_apa_YKvTAb1Q517NP