It actually isn't too hard tapping an oil pan. We tapped my friends pan ourselves when we supercharged his V8 Dakota. You just have to use a step drill and use plenty of lube to get all of the shavings out (we did it while the pan was still on the block, in the truck). And a good amount of Teflon tape, lol.
But yes, Moroso makes already tapped pans, though they can be quite pricey. I was lucky enough to find an oil pan locally that was already tapped, and was welded.. very nicely. You can also look for something like that.