Thanks Bill. I was actually able to get the part numbers from Compnine (love their VIN decoder, too!) and surprisingly GM Parts Direct still has the parts available. For other members benefit, the parts are as follows:
25544906 */STR-R/D (passenger side rear door)
25544907 */STR-R/D (driver side rear door)
I have two Bonnevilles (1993 and 1999) and these moldings need replacement on both vehicles because the metal substructure to the moldings has rotted on both vehicles. Looks like a fairly common problem and the boneyards probably are in poor condition as well. Thanks again!