You'll get drag tyres in many sizes...but 14" is not one, even for competition type tyres 14 would be odd.

13" yes, 15" yes, 16" etc etc

Even that M&H is a bit of odd size, I'd defo be giving the guy a call, as to buy a pair of most tyres from the US ends up bloody expensive
And most drag tyre tyres will aim for diameter of 26" and above as some class racing there just goes by tyre diameter so 26", 28" etc are just common sizes.