David Lesher wrote:

I've been on a snipe hunt for a vibraplow
http://ditchwitch.com/trenchers-plows/walk-behind-vibratory-plow/100sx-vibratory-plow/
in the Santa Cruz region. I've yet to find a tool rental outfit
that even knows what I'm talking about... Yet on the East Coast,
they are common...

Any suggestions welcomed.

Try one of the big rental companies with a national presence? At least
they should have a reference number for the item from the east coast so
the folks on the west coast who call it something else can look it up by
number. Perhaps other terms like "cable plow", "sprinkler plow" or the
like. A call to the Ditchwich folks might tell you the rental yards in
the region that carry it.