Then you want Mike S. @ On Target Technologies (OTT) firstname.lastname@example.org
Mike can easily do the job for you.
Leupold is my first answer. To my knowledge they have the longest best eye relief (other than Night Force-which is too much money for you currently) at high magnification.
If it is 20 power you want then start looking up the specs of rifle scopes in the eye relief distance at the highest power or 20x. Then compare and make your decision based on your finances.
For a fixed power scope the 20x Super Sniper may be the answer to having high power and keeping it in the $300 range.
I need to know what distances you are considering?
Also, the 3-12 Burris LER is a great handgun scope. It is my top choice hands down for the LER's.