If you could get the neighbors to contribute some money or you live in an area governed by a community association, United Rentals has the radar trailers for rent.
If not maybe the local township/city council could give you a grant to rent one.
Our Auto Insurance company loans out portable speed watch devices to community groups for a week at time to track speeding on residential streets.
Maybe some of the big auto insurance companies in the US like Allstate, Geico, State Farm have the same program.
