Myself and many others have put a used Honda CRF 21" wheel on the front, and there are a lot of choices of 19" for the rear.
I have a Tusk T35 100/90-19 on the back, but I would recommend finding a softer/gummier rear tire.
Of course that depends on where you ride.
Any Honda CRF front wheel will work provided it has the 6 bolt pattern for the rotor, where there are 3 sets of 2 bolts close together.
For spacers, you use the stock Honda spacers, and add an additional 6mm spacer on the right side and stock Ultra axle.
You can find used CRF wheels on ebay, with and without tires.
Example:
165963147349 for sale | eBay
And regarding the traction control, you only have to transfer the slotted rings to your new wheels to preserve the traction control.
With that said, I never use it, I did some tests on a challenging hill climb, and consistently had better results with traction control turned off.
One thing to know about the Ultra, there are no rimlocks from the factory, so it's just a matter of time until you rip the valve stem out of the rear tire.
I have a 19" tubliss in my rear tire.
The Ultra is a GREAT bike for the money, but the range is less than 25~30 miles, which is OK for tough single track, but not enough for places like Hatfield McCoy.
In case you didn't know, the Ultra has REVERSE, which sounds weird, but can come in VERY helpful at times.
EDIT: I recommend these handlebar risers in black:
1 1/2" Barback Risers for 1 1/8" Handlebar (BLEM)