Replacing soft top
 

Greetings from Richmond VA!
I am on my second Miata, and generally have let my mechanic take care of any problems.
However, my current Miata, a 1993 and probably and NA, whatever that means, needs a new top and I jumped into the fray to help find a new top that won't cost me an arm and leg.
I am pretty certain that I want a vinyl soft top (Cabrio?), with rain rail. I have been told Robbins tops are the best. I ahve also heard that Sierra is good, but I've seen reviews to the contrary.
Is it advisable to avoid ebay or amazon, when buying a top?
(PS-I will not personally be installing it. My mechanic has put a top on his own car, so I trust he knows what he's doing)