The Re-Pop parts are manufactured all over the place. Some in the USA, and most I would say are from off shore. As far as pin pointing a lot of the parts down to a specific manufacturer, that is difficult because many parts are made by the same few companies and the retailers sell the parts in their own packaging. Do not believe for a second that all the retailers are making their own parts, that is a nonsense!
The obvious parts which can be compared to another easily are the soft trim parts, most are made in the USA and of course there are a number of manufacturers of weatherstrips which are always up for discussion.
I find it very interesting that after all these years of having re-pop parts available there are so many problems with the quality. GM should have continued making their own parts and we would all be a lot happier, even though some of theirs are not that good also. JMO