Dvor (optics planet sister company) carries the on and off.
I just checked, and they have it on sale right now. $229 for the red at $265 for the green. It says either version ships in one to two days.
https://www.dvor.com/holosun-opmod-hs507c-x2-reflex-red-dot-sight.html?promotion=opmod-optics-and-more-56-2024-05-10I've only placed one order with them in the past, and optic, and it did arrive quickly and I was satisfied. I have definitely read some bad reviews about optics planet and them not having something in stock but still taking the money and making people wait for months.
That being said, I was contemplating getting a gray 507 and would probably order from Dvor when they have it on sale again.
I thought about getting it to go with my gray Grit Grips Glock 19 frame and my gray PSA Dagger slide. That was when GT Distributors was selling a gray Streamlight TLR1HL for $150.