It's apparently amp trim of all things.
Vinyl Welting | eBay
It's starting to show up as 'interior automotive gap filler' in auto stores like Pep Boys, but it's 3 or 4 times the price of getting it on e-bay. Getcha any color you want. Also looked pretty good wrapped around the knee padding on the center console, but I don't think I've got enough to do them + the new car so may have to order some more. Total install time, about 3 minutes.