Been googling... and I may have found a product that might allow me to bond polypropylene:
http://www.nbond.com/techdata.html
The problem I had came from this fact: polypropylene is a "low energy plastic", aka a non-stick plastic, much like Teflon.
http://www.nbond.com/faq.html#lowen
On the plus side, cyanoacrylate (superglue) might work too.
Still searching...
edit:
e-mailed 3M and Lepage.