Here's two mounts that you will need. It attaches to the front, lower rail. You'll need one of these to attach a red dot properly.
https://www.opticsplanet.com/um-tactical-um3-sight-mount-for-universal-rail-mount-style-black-finish.html https://www.opticsplanet.com/german-sport-gun-1911-ad-ops-bridge-mount.html I have a couple from different manufacturers that don't seem to be making them any longer. Yes, they do raise the scope / sight (I use them with red dot sights), but once sighted in, you learn any hold-over that you may need when changing shooting distances. Or...readjust the sight.
I have this style on both, pellet guns and powder fire weapons. So far, I've had no failures with the brands that I have.
I have one like the blue one above. It fits a little loose. I had to do a little shimming to get it tight. After I did that, all is well. you can take it off, put it back on and the point of aim is still the same.
The other style fits tight as is. Some may take a bit of a hard shove to get it in place. Again, they are pretty solid, and can be removed, reinstalled with no change with the point of aim. One like this that I have, like I say, are a tight fit. But once in place, they do not move..!
Look around, you may find more,
As for the sight itself, there are MANY...to choose from. Go to Optics Planet, type in "red dot sight", hit search. You'll have hours of searching ahead of you. Me, my top red dot is the Holosun brand. Then the Leupold, Delta Point Pro. Vortex is a very good brand. You need to look at the hours that the batteries will last, and the warranty before putting out your money. They go from $30 (I would NOT buy), to over $1000 (I also, would not buy !). This is another item that the cost goes with the product.. You can buy three or four cheap ones over time, or buy one quality one for a few bucks more.
Mike
P.S. - I have the same P-226.