Since the .38 National Match pistols are uncommon in and of themselves, finding a slide and barrel alone seems very unlikely. On the other hand, who would need one since the pistols are few? Therefore, if you could find one, you might not have to pay much for it, since the demand would be low. On the third hand, if you need it, you will probably pay dearly for it.
Maybe sell the ported pistol for what you could get and buy a correct one? The cost would be the same or probably less, and you would not have to search for years.