I've redone a couple of SMB's but I can't remember where I got the material. One was a member here's van and I ordered everything in for her. It had about a mile of that stuff in it, all shrinking and dying a painful death. If I ordered it from SMB I would've gotten it from Nancy at SMB North. If I got it anywhere else it would've been from these guys:
It is a really bad idea on SMB's part and it ALL shrinks up comes loose. They didn't have much choice though using f'n MDF for cabinet material. It's not solid enough to hold any kind of groove molding for long.
On vans I've completely redone the cabinets in I use 3/4 birch ply and regular T molding (semi-rounded edge) and use Liquid nails or any construction adhesive in the groove before I apply the molding. As far as I know none of that has ever come loose.