Bali, if you have no luck from Buds Benzs,ill will give you a little help.
You know now the size seal you require,as you said you already purchased one ,but was to small.
Over a time of 30 years i owned about 12 Buicks, Cadillacs, and other foreign makes and models,many convertibles,
and many classic makes and model seals from one make of car will often fit another make, example Fiat spider ,some fit
Alfa Spider,. Cadillac some will fit Buick and Oldsmobile.
One of the best sources for all classic cars is a company called ,--Steele Rubber Products,www.steelerubber.com
out of Denver ,NC. 845-462-5959 go on line,and check out Cadillac first,especially there trunk seals, i think you need about
14mm x 20-25mm and with small lip that you require i think, you will know when you take a look ,as steele has close photos and sizes,and they will even send you free small
samples.
They have thousands of seals,another good source is---Old buick parts---they are out of New Jeysey also hundreds of seals
to select from,both very good reliable companys that have been around for years.
About 1988 to 1994 i spent over $ 2500 from Steeles Rubber seals.----regards.