EZ makes a good suggestion, but check the dimensions of your seats carefully before you buy any after market replacement seats. Searay boat seats of that era are usually much larger and wider than todays after market back-to-back loungers.
Agree with the above poster...problem with 90% of all back to back aftermarket seats are the bases are only 10" high. On a 23' boat you are going to feel like you are sitting on the floor....I'd look for 16" high base min .
Great Lakes Skipper seems to have some oddball, surplus, and "one of" OEM items. Check out their web site or maybe give them a call to see what they can locate for you. They seem to be somewhat like Odd Lots or some of the other surplus stores.
now you feel my pain,,, most of the newer ones i have looked at have 10" base heights, cant find any that are higher than that. been looking hard, for a while. kinda stuck in between a rock and a hard place