If you're looking to buy a vibrating screed, you can get a good one from Amazon, the Tomahawk vibrating screed, it comes with a 12' board and a Honda motor. An excellent screed in my opinion. Well, those are what I feel are the two best types of concrete screeds. The 2x4 screed for it's simplicity and easy learning curve.
Morrison Concrete Screed 500 (Ashland) Morrison aluminum vibrating concrete screed. Six 5' sections for a total connected length of 30'. Can be set up in increments of 5' for pours. This screed is adjustable to create crowns or different contours. The Wisconsin engine will run but the gas tanks leaks as well as the carburetor.