i think that's just one of those things that you're really better off going for another truck if you want it. Or at the very least swapping the entire cab. You'd either have to cut the roof metal off, and reweld a sunroof... roof.. Or make the hole yourself and hope it seals.
Then you'd also have to replace the inner headliner install the sunroof hardware + motor, install the sunroof switch, and run the new wiring down to the fusebox. Plus the drain hardware Vaegleav mentioned.. All in all.. yeah.. again its matter of time and money I suppose. Roof leaks aren't worth the risk if you're not willing to shell out the money to do it right imo. You're basically taking the entire roof out and replacing it with the other truck.