My Local Pool Store, that is an above ground dealer has some of these in stock. It may be a good idea to try HD Supply or some of the other more commercially focused stores for these larger sizes. It will all depend on you local market.
Not sure if I understand correctly, but I believe that you are looking for something like this? If so its a Hayward SP729. I'm pretty sure that I got one at Leslie's, but I'm sure you could find a source online that might be cheaper.