I have not seen one for the DX sight. I know that Tooltech ( http://www.tooltechgunsight.com/index.html ) will do it, but you probably have to supply them with a blade. They have done several pinned blades for me, but I supplied the blade. You might want to email them and ask. If you do, let us know what you find out. I'm thinking about night sights for my 686SSR.
The Interchangeable Front Sight system is still in use today on firearms like the 627. I think that SDM made the tritium sight that is pictured on the revolver in the upper left corner. You might want to give them a call.
The rear Tritium blade that I used on the revolver came from Meprolight.