The GO 200 does use a brass T-Nut due to the added thickness of the EVA deck.
Any Starboard dealer should have some in stock to sell you.
If you don't have a local dealer, try the Starboard Distributor for your country or area.
If you don't find a Brass T-Nut at the above sources, send an email to Starboard HQ
in Thailand and they can most likely sell/send you a new nut.
Probably smart to get 2 of them as then you will have a spare.
Let me know if you are in the USA, I may be able to find a way to send you one.