You could siphon the water from the stream, but the deer scarer would have to be lower than the point where the stream water enters a pipe of some sort. Check out solar powered fountain pumps.

I know this is an older post but....

if if you plan on putting it neat the stream anyway, why not use the stream? Bu this I mean use a water wheel. You could use it to create your pump electricity, but better yet would be to use it as the water source itself. Do this either directly with utilizing the wheel with scoops to pour directly into your scare, or to fill a sluce to carry the water to your scare.