The rear cradle insulators are no longer available for the Buick Reatta. The following information my help someone who needs the rear insulators.
fordrodsteven, member of the AACA forum wrote:
"I ordered and used P/N 3538757 (insulator) from GM Parts Direct. They were less than $35.00. They are listed for 1999 Caddy Deville but they are an exact fit to the Reatta. Before that I ordered the Reatta P/N and I got the metal parts but no rubber insulator material. This P/N 3538757 comes complete ready to bolt in. It has the metal component and the rubber insulator material is bonded to the upper portion. If I remember correctly I used the same bolts as used on the front cradle bushings. P/N 11517635. I think I had to order the lower metal component also P/N 25678602. It's called the "spring insulator""
GM part # 3538757 is part #8 in the illustration below. The illustration is for the rear of a 1992-1997 Cadillac Edoroado but several other Cadillacs use the same part.