I have this rifle:
Bushmaster Patrolman's Carbine A3

I was thinking of putting an EO-Tech 512.  I would also like a rear flip up sight.  My questions are

What would I need?  

Who makes them?

Thanks

You can order the EOTech and a Bushmaster flip up rear BUIS from Bushmaster. The flip up BUIS is actually made by YHM for Bushmaster. We have 5 of the BUIS on our patrol carbines, and I have one on my personal carbine, which is also set up with a optic. Good Luck Hope this helps.
The EOTech will cowitness with your front sight, you won't need any other bases or mounts to have this set up of front and rear BUIS cowitness.

www.ar15.com/forums/topic.html?b=3&f=18&t=206233
Here are pics and links to BUIS systems

Thanks for your help.
I just recently saw the Bushmaster flip up sight.

I like the ARMS sights.

I have a DPMS Mangonel Rear mounted on mine.  Lays quite flat, and flips up easily.