This isn't true cruise, but check out Go Cruise. I think it's http://www.gocruise.com
but if not, just google it. It's only about $20 and grips your throttle and braces against your front brake lever. When you are at the speed you want, just push the device against the brake lever and it will hold your speed. Obviously in doesn't change the engine speed on hills or have a resume like real cruise, but for twenty bucks it's sure better than nothing. There's a video on the website which is much better than my description.