For $81+/- on Amazon, the OP can buy the excellent Bushnell trs-25, which works great and comes with a lifetime warranty. I'd recommend buying a short riser through Amazon, as well.
The so-called "debate" about mounting plastic on gas blocks is silly. I sometimes heat up my ARs pretty well, and I'm not going into combat. I did use a railed gas block on one of my builds, and I quickly discerned, with no instructions or lecturing from anyone, that it was stupid to mount anything plastic on a railed gas block.
The chances of my ever using one of my ARs in a s.d. situation are somewhere between infinitesimal and zero, but probably a lot closer to zero. I still wouldn't want to mount a piece of polymer on my gas block. And, yes, some polymers, of course, do melt.