Not a saildrive but maybe a place to start: http://www.rayeo.com/motors.htm
There is also a Briggs & Stratton electric outboard with grunt - not sure if it is still on the market.
I have a design for a 48V system using a Perm Motor PMG-132, Sevcon controller and a ZP3 right angle drive. http://www.electricvehiclesusa.com/category_s/69.htm
The brushless motors spin a bit too fast for best results with typical legs. Here is a kit: http://www.electricmotorsport.com/st..._drive_kit.php
You can buy Yanmar saildrive legs (do not know the cost) and they would match the Perm Motor reasonably well as they have 2.6:1 gearing.
I have not seen an off-the-shelf saildrive yet.