Note also that the stems can be mounted "upside down", changing the resulting handlebar position somewhat.

And, if I'm not mistaken, while the riser tube is a part manufactured for the Swift, the stem is a common off-the-shelf component -- I expect there are many choices of "1-1/8inch threadless stems" that would work on the Swift, with varying lengths/angles/materials (some even with adjustable angles). You may find a 3rd party stem that does better for you than the particular ones Xootr offers.

Xootr has more information on the seatpost, stem, riser, and resulting distances for various combinations, on their Frame Geometry page. They also point out the risers can be trimmed to shorter lengths (so you could make an intermediate length by trimming the longer one).

For what it's worth, I found that replacing the stock handlebar with one a couple inches wider, and slightly swept back, made a substantial positive difference in the bike's handling for me (and that also changes the distance to the handgrips).