Ask around at your LBS' , the mom and pop type shops, they should be able to point you to one. Any competent welder with a gas torch should be able to do the job. Buy some track ends somewhere first. The trick is to get the angle of the slots correct, which could easily be set up if you bring the bike with the tires and wheels attached so the guy can see what the angle needs to be to get the slots horizontal. Check the yellow pages.
But why bother? Any amount of adjustment room in horizontal dropouts should be enough. My world sport came with only half the length of slot available, a dremel and round file was all it took to open up the rest.
A road geometry bike with track ends only makes you look like a, what, posenger? jmho. To each his own.