I know this is the internet but I'm going to take your word that you're a disabled vet on a limited income. I'm a couple of years younger than you so lucky for me my draft card didn't get called before Nixon ended the Vietnam war.
I rummaged around through my parts and found one of these that I don't use anymore.
http://www.midwayusa.com/product/655...le-mount-matte
I flipped it around in the mount and it works on an ar, if I remember it even cowitnesses.
PM me your address and I'll send it to you free, it's just taking up space here. I checked it out and it works, still has battery life. Even if it doesn't work for you at least you'll get a feel of having a red dot on your rifle.