https://www.newenglandcustomgun.com/pro ... ?prod=4200This is the only thing I have ever found that is anywhere close to what you’re looking for. If somebody were to make a notched sight like what you describe, I bet they would find a market.
The NECG would have to function as a ghost ring, given the distance between the rail and the receiver. If you’re interested, take a look at the Weaver mount version. It has an extra-low add on that might suit your needs.