Bentonite as a liner?

I've just finished digging the hole (yay!), and am preparing to order the
liner, i orignally planned to just go with a good ol' plastic liner, but the
neighbor's handy man came over to check out what we were doing and he
suggested using bentonite clay as the liner rather than a plastic liner.
I've done a little research and it seems like bentonite is more often use in
large ponds. i'm just wondering if anyone has experience with bentonite or
if they know if it would be good for a small back yard pond. The hole is
about 27'x18' at the largest points. Also, if it is a good option, does
anyone know where it can be purchased, preferrably somewhere in , around or
near (Eugene) Oregon. Thank you much!

Megan