Just a additional link for SpyderHere are a few options:
I have friends that have used the friction type. They are simple, but the downside is they do not maintain speed... you speed up going down hills, and slow down going up hills.
I had electronic cruise on my last Honda Goldwing, it was very nice... worked like my cars cruise.
It might be worth contacting these folks to see if they can do something for Can Am Spyder diameter grips/handle bars. My experience is a lot of these type people will work with owners of new "cycles" to develop their products.
Here is a link showing all the components of the above friction type cruise control:
It says it fits 7/8" to 1" handle bars.
This site has many interesting options: http://www.mccruise.com
Note they manufacture a unit for Can-Am four Wheelers: http://www.mccruise.com/Bombardier-Traxter--Traxter-XL-Speed--Spray-Control-p-4.html