Interestingly, I posed this question on the Ask Andy forum about a week ago. My quest was for the thick MOP buttons like those on Borrelli shirts. There was only one reply, and that was from Alex Kabbaz, indicating that he sells them. Here's the link:http://www.customshirt1.com/PearlButtons.htm
I don't know where you live, but if NYC is within easy driving distance, you could check out a store there dedicated to buttons! It's Tender Buttons
. They too have the 3.2 mm. MOP buttons that Alex has, but they don't appear to be set up for online sales. Good luck!Edit:
Oops, now I see you're from Houston. So forget Tender Buttons.