Check these Drew:

http://seattle.craigslist.org/kit/boa/2522097829.html

This roberts rigger fits into a Fish-On style rod holder mount:

http://seattle.craigslist.org/sno/boa/2518532853.html

Another cheap one, Cannon sells clamp mounts:

http://seattle.craigslist.org/see/boa/2511688963.html
_________________________
When I grow up I want to be,
One of the harvesters of the sea.
I think before my days are done,
I want to be a fisherman.