Something like this, perhaps?
American Tactical Imports

ATI uses a polymer lower receiver that is a plastic overmould of a metal insert that reinforces where the buffer tube and rear take-down pin is located. There is no metal-on-metal contact at the take-down pin in the front.

Given the prices on competing all-metal rifles like Ruger, S&W, Bushmaster, Stoner, etc., my personal opinion is that you would probably be happier in the long run with a metal lower receiver even if costs a few dollars more.