Fixing a BMW tank bag

Strange thing...i had a multivario bag shipped to me, in great condition. However, it was packed in styro peanuts, and the foam on the bottom of the bag disintegrated (heat/condensation?) like chocolate cake.

I did my best to scrape it all off, but now there are some holes/tears in the vinyl and tons of old glue. Am i better off taking it to get a new piece stitched in with foam, at an upholstery place? Or can i just patch it and glue a new piece of close-cell foam in place? I would think glue-glue isn't a good bond. Thanks

I went to the local dive shop and got some scraps of neoprene and wetsuit repair glue.

Go to an industrial rubber supply house and buy some closed cell neoprene foam, 1" thickness is good. Get some Weldwood (Home Depot) contact cement, and a cheap throw a way brush.
The foam will cut very easily with an electric carving knife, just don't let the wife catch you.
Cut the foam to fit, coat both the bottom of the tankbag and the side of the foam that will go the the bag with the contact cement. Let both pieces dry to the point they are just barely tacky, then press them together. Dont worry about the old glue, if you couldn't remove it with scraping, it won't be an issue.

thanks guys!