Thanks for the find, Steve. It is called a Sprinstarter and seems just the thing that the original poster was interested in. They make one for my boat's engine (Cummins 5.9L B series) so I sent them an email requesting a quote. Haven't heard back.
We don't have a "spare" starter motor and among all the other budget items, that spare was one of the things we were planning on buying in 2014. Therefore, having a Springstarter could be our "spare" instead of the actual starter spare if the Springstarter is reasonably priced, etc.