I installed aftermarket Audiovox electronic cruise on 3 of my ST1300's for about $100 each and grew to love them. Never had a problem and I intend to do that with the S10 eventually.
In the meantime I have the Kaoko throttle lock and while I have never been very fond of throttle locks and at first found this one to be a bit fiddly to engage, I learned that it can be a great help on long trips. My son and I recently did 4500 miles on a round trip to Colorado and that included lots of miles and miles of nothing but miles and miles while going thru back roads in Texas, parts of Kansas, and Oklahoma. On those long stretches of lonely roads, I found that with the Kaoko, I could adjust the tension so that it held pretty steady on fairly level stretches, while also allowing me to gently roll on or off slightly as the terrain changed. Unlike other throttle locks that I have had that are either locked or off, the tension adjustment can be made with my right little finger while riding, just adding or subtracting a small amount to suit the situation, so that I could then fine tune throttle position as I rode. Not a true cruise control, but not bad.