I have spoken with just about all of them. Bill Potter is actually in the business now he makes an all glass one that is much lighter than all the rest. It is a bit expensive but not much more than comparable aluim models. Here is a link to them:
Seamark/Hermco
Other then them here are you other alternatives:
Armstrong
Gill
B-Bracket
seamount
<a href="http://www.dadmarine.com/index00.htm" target="_blank">Dad's
Marine</a>
Stainless Marine
I found Stainless, B-Bracket and Gill, tough to deal with. They did not want to bather with a small guy like me. I may have caught them on a bad day also.
Hermco was fantastic, he is actually a member of this site, seamount was also nice and priced well, I have yet to contact Dads but they seem very well priced and you can get them unfinished so if you are re painting your hull you will be able to get the bracket to match perfectly.
Keep us updated.