Ditto on the nylon flat head black machine screws for all Lexan. They have held in the F/G for 4 years. F/G threads are just fine after dozens of in and outs.
95133A394 mcmaster carr. you might want to get an assortmetn of 3/8, 1/2, etc depending on the location. Or buy 1", chop and re-die.
My...