I checked our database to see if the U5 batteries are compatible with the newer U6, unfortunately not. Usually manufacturers and third parties do not manufacture batteries for new models since they do not know the specifications (and there is no market for them yet).
I do not think we have any in stock. Although we may be able to make one for you. Please follow the instructions on the bottom of the Help/Info page http://www.topmicrousa.com/aboutus.html
I will get one of our employees to assist you as soon as possible.