I have a '90 300SL and I purchased, thru Ebay the late glass top from a '96 600SL. It fits perfectly with NO modifcations (yes NO modifications) and does NOT leak in rainy weather.
There seems to be an abundance of tops coming from Florida. Quite pricey at a minimum of $3000 upwards I think it is worth every penny and if u sell your car u can resell the top separately at a profit. As u know they are rare and in demand. Just keep checking and Good Luck and Hope that helps your search.
Hz