Just go to images.google.com and do some searching. I searched for "stopwatch line drawing" and got lots of suitable results. "alarm clock line drawing," etc., will probably get you more.
Of course, I don't know what images are copyrighted, etc., so you're on your own there, but there's probably some free clipart in the results.
Technically, they're "all" copyrighted. It's just a matter of what kind of license you have to use it. Why not create your own? Shouldn't be too difficult, and you probably wouldn't have any potential legal entanglements.