One of my RDFs died recently. It seems to be something they do. Anyhow, I had a red dot rifle sight sitting around doing nothing, so I removed the mount from the RDF and cut a plate from a bit of aluminium sheet to fit the mounting on the sight. That screwed to the top of the RDF mount and presto! A new RDF!
In use it seems to work fairly well. The LED is variable brightness red or green and the fact that there are two layers of glass doesn’t seem to dim the image too much. It does suffer a little from dew though, so I need to make up a proper hood for it.