Magic Pie 5, Magic Pie Edge and Smart Pie 5 now available with Bluetooth connectivity for setting and monitoring.(Bluetooth connection requires Android 4.4 onwards)
If you can't think of any good reason to get a rear wheel kit instead of the front, this ought help! You can even make your own!An added bonus is that you can mount a slew of batteries on the bottom of the cart.
Here is another one like this I saw about six weeks ago where the guy cut the bottom off and mounted regular front wheels with the forks on the sides of the basket which made it impossible to steer over 5 miles per hour. The rest of it was done pretty much the same.