Hmmmm....Obtain a new one if disired....peal that stuff off....While replacing it inspect for rust....If there is any get it fixed before it's too late. Ask me how I know.... Oh you should check out LMC trucking....they will probably have it...it's ok stuff.
you can still get them from gm parts direct for like $ 30.00 . But your better off just having a windshield technician come out and re-seal it and put a new universal seal back in . Check your local craigslist for windshield installers . I'm able to get new glass and seal for $110.00 here in Denver
FYI GM Parts Direct is just a stealership posing as an online website. It's their parts department. Same with GM Parts House, GM Parts East (great people & prices!), etc etc. Just buy local dealer.