Try Flounder Pounder Marine......they buy a lot of left over and obsolete parts from the Sea Ray factories, but on a 30 year old boat there isn't much chance they will have anything.
Your best bet is going to be the retail department of Teak Isle here:
http://www.boatoutfitters.com/boat-sliding-door-hardware.html
Most likely, your door assembly was produced by Spartech Marine which ceased opeations in 2008. Their lead parts guy was Ben Marks who now works for Flounder Pounder., so that is a phone call worth making even though they probably won't have what you need. Ben can probably enlighten you and steer you in the right direction.