Only half way through this project but since I will not be finishing it any time soon due to lack of a driver I thought I would post my progress so far any way.
The Aspheric is a 44mm lens available from DX in a 5 pack.
Its nearly a perfect fit in a D sized mag. I said nearly. I made up a POM ring to hold the lens central.
LED will be a SST-90.
Mods to mag are pretty standard for a Mag diving light.
Heat sink is a slip fit with bored out rear to take driver.