For hop-up unit and rubber Prometheus is from what I've heard a great brand.
- Prometheus Soft rubber
(If your field limit is 400 FPS or lower otherwise a hard rubber will do the trick)
- Prometheus hopup unit
I got these links off redwolf but I'm sure you can go to airsoft extreme or the warstore or something and get the same stuff. Also redwolf is out of stock on those hop up chambers/rubbers so you'll have to source them out from somewhere else.