I have 2!!
One is an ancient Lowe Alpine waist pack. It’s just a simple single compartment with a zipped pocket for keys.
The other is a North Face Mt Biker which I use for longer, wetter rides. It’s bigger, with two separate, zipped compartments and two mesh side pockets for holding water bottles.
HERE
To be honest, TNF one is a bit on the big side and I can cram a lot in there. For example, I’m out for a ride after work tonight and I was able to easily fit my lunch, work clothes, tools, pump, wallet, phone, water bottle etc etc with my coat strapped to the top.