The best I've found is either CousinsUK.com (Go to watchparts>Branded>Omega>Case parts and search by Ref Number "145.036".
Now the second best has been http://cgi.julesborel.com/
Cousins tells me its a: Glass, Mineral, Omega TN5250
It appears to be a flat mineral crystal.
Some of the photos make it look like a domed crystal.
Either way genuine is around $60USD: https://tmwatchco.com/product/new-genuine-omega-flightmaster-crystal-145-036/
I wouldn't stuff around with an aftermarket on such a watch unless you are qualified to measure and size one up yourself.
Super glue is some funky stuff.It works but I have found that occasionally it will get deposited by vapor,and that these can only be removed by acetone. Additionally sometimes the things you want to stick together don't and the things you don't want to stick together do.