Interchangeable GM keyless remotes?

I need to buy a new keyless entry remote for my car, but it's been hard to find the exact right part number on ebay. (My part number is 12522338, for a 1990 Olds.) How can I find out whether I can use a Chevy, Pontiac, or other similar 3-button remotes will work on my car. Another thing I wonder about is why some remotes have the trunk button on the bottom and others have it on the top-right.

Try searching for the new superceded part number.
88959920