The cork isolation pads under my A/C condenser unit have disintegrated. I am looking for a replacement. The DiversiTech MP-3E (3 X 3 X 7/8) looks good since it doesn't have a cork core. PexSupply sells 4 for 3.96 but the shipping is 11.61. Any suggestions for another pad suitable for outdoor use? (Not hockey pucks or cut up old tires.) I would like to buy locally but I haven't found anything at Lowe's or Home Depot and Grainger's are expensive.