The ribbon switch made by TapeSwich, has an operating force of about 8oz.
This should be suitable for most mowbots. Ribbon switch can be cut to any
length and then sealed with a special terminal block.
I have emailed their sales department and will post the prices and details
(like bend radius) when they arrive.
My own bumper switch seems to require quite a bit of force (around 2kg) for
reliable operation. I am considering changing to the ribbon switch if the
price is not too severe.
Dave Everett
Mowbot Project Website
http://www.idx.com.au/~deverett/mowbot/index.htm