Specialty Aluminum does very nice work. I don't know anything about the others you mentioned. It may be out of your way, but Glenn at Custom Marine Concepts in Spring did a T-top and shortie leaning post for my Seaark for a very reasonable price and they were works of art. I've also seen some of the work done by Coastline in Seabrook and they do very nice work.
As far as a folding or removable top, it would probably be very labor intensive and expensive so you are likely going to be stuck with one of the pre-fab ones. I had one on my previous boat and I was very unhappy with it.
The manufacturer may be a sponsor here but I will be happy to PM you about it and it's shortcomings if you are interested.
If you can live with a fixed top, there are some very good options out there.
2015 Seaark 1872 MV CC Etec-90
Helix 12 CHIRP SI, HB 1199, MinnKota Riptide ST80/i-pilot Link, Bob's Hydraulic
Bitter Gun Owner