The kit that I think you need is APK01. The seal that I THINK you need is in this kit and is octagonal shaped with part that seals off a corner. If you go look at the picture you can see what it looks like then check yours to see if that is the seal.
To look go to: www.aircondition.com click on Straight to the Board, then click on AC Source at the top of the bulletin board page. One of the selections will be O-rings, O-ring assortments......