For anyone who has lost one of the clamping knobs used to adjust the position of the windshield (I'm sure that you can guess by now that I have), I have found an almost identical replacement online. The only difference I can tell is that this particular part has brass threads, but it held up fine on a long off road trip.
Part number 6332011 on the third line of the chart. they are only $1.28 each, but they will charge you close to $7 in shipping unless you order $20 worth of stuff (then shipping is free). So I just ordered 16 of them (4 for $12 vs. 16 for $20.50).