MZ Miami or ZedaMotorsports.com
I don't think either are stocked at the moment but zedamotorsports is supposed to have them back in stock in 2 weeks or so..don't hesitate when you see them in stock...they sell out rather quickly.
Moderators Note:
Please be aware that Zeda Motor Sports and Robert Bianchi have nothing to do with Zeda itself which is a manufacturer of Zeda Motors in China.
A reputable vendor of the Zeda line of motors can be found at bicycle-engines.com