Red dot for Hellcat

Back when they were hard to get, I settled for a Romeo Zero @ $200.
It works but it's not ideal, you can still use the the irons but you won't have full view of them.
You also have to shave down the mounting screws per the Hellcat manual. This isn't hard to do. I put the Allen key for the screws in a vise sticking straight up, put a screw on it and filed it to the proper length.
I do like the "shake awake" feature so you don't have to turn it off when are not carrying it or shooting it. But it does not have auto adjusting brightness so you'll have to find a brightness that works for you both in bright and low light. My solution is to leave it set for bright light and use a rail mounted flashlight in low light. The light and red dot work great together. The flashlight is an Olight mini Valkyrie 2.
Good luck on your search.

I also have a Romeo Zero on the Hellcat and concur with the above. The small size of the sight goes well with the pistol...looks like they are made for each other and adds little weight.

Joe Bob outfitters had the Romeo Zero on sale for $150, worth seeing if they've still got any, mine came last week. It worked great in my Hellcat, shot it for the first time today. Its not my favorite red dot design -- need to remove the sight to change the battery, non-click adjustments that need an 0.050 hex wrench. But the small size and light weight overcome these deficiencies for this situation. Another plus is the Romeo Zero sits low enough that you can still use the stock iron sites as a "back up" which also really helps when making zero adjustments.
You will need different screws (or modify the SIG supplied ones) to mount it on your Hellcat.

I found the mid level brightness was fine at the range today on a very bright hot August day.

Hellcat with red dots-