I use and can recommend products by CRSpotless.com They sell several sizes of de-ionizers, along with bulk resin. Definitely not cheap, but extremely effective. I have the DIC-20, which has an electronic purity meter to indicate when the resin is getting depleted.
My local water is quite hard; around 30 grains of hardness! After washing, I can perform a final rinse on a black vehicle and never have any water spots, even if I park in direct sun while drying (tried this for curiosities sake). Be sure to use only for a final rinse, as the cost per gallon is really high!!
I've also used the Mr. Clean device years ago and it did work pretty well, it just didn't have much capacity.
But after saying all this; I prefer to clean my Street Glide using Zaino Z-6 quick detailer whenever possible. If my bike is not terribly dirty, I throw it up on a jack and CAREFULLY clean with several microfibers and plenty of Z-6. Takes a bit of time, but I don't have water drips to dry off later, and the quick detailer helps to prolong the paint sealant (Zaino Clear Seal), too.
Not trying to sound like a shill for either company; just mentioning what works well for me ...
Mike