There seem to be a number of them around, from economical to expensive. I still use iron sights myself, but as my eyes age, I may change my mind at some point.
this one is at the economy end and has a threaded small plate that fits a standard 1911 sight dovetail, and the main optic plate is then screwed down to the small dovetail plate.
These appear to be similar but more costly, and I found
still more expensive ones. Just Google "1911 Sight Plates," and you will find a lot of options.