Jaeger,
As I said, the Billy Bunker has issues as well and you are raising one of them.
The other product I was trying to recall is called Bunker Blinder. It is made with rubber chips and adhesive. Basically it is mixed and then spread on the bunker floor. It works similar to the Billy Bunker but is touted as stronger, longer lasting, and safer for golfers. I have yet to use it at any of my projects but might consider it if forced to use a liner (sometimes the Club/Superintendent overrules the architect).