I am not sure if someone mentioned it here somewhere and I just missed it but...
Polymer can be laser engraved. I just got mine back and it looks just as good as any metal lower I have ever had laser engraved. And I have had several done. All done by Bill Gray at Gray Laser Engraving.
Bill Gray at graylaser.com in San Antonio, TX can take care of you. I called him to discuss it. He said after doing several hundred of them he has pretty much gotten the "laser power" dialed in and can do them no problem. I am sure your desired engraving location can make a difference, but he can tell you what's the best way to go. He told me that the location can make a difference because the thickness of the polymer varies based on location. No surprise there, as I expected that.
I sent him one on Monday (I used FedEx and he got it on Tuesday). He completed the job on Wed., shipped it out on Thurs., and I got it Saturday (he used priority USPS for return shipping.). So, it was 6 days door to door. 55 bucks plus return shipping.
They are good people. His wife will likely answer the phone, as Bill is usually on the machine working. Good work, good price, and most importantly to me, FAST!!!!
Anyway, just another FYI.
Regards,
G.