Need ideas for spotlight transducer

My HDS came with a rebate for a spotlight transducer, which is basically a trolling motor mounted forward looking transducer. Neither of my boats or yaks have a trolling motor. So I am trying to come up with a compact design to have 12v motor rotate a shaft 120 or 150 degrees in continuous cycle. Sweeping back and forth. Best I can think of is a wiper motor and arm setup. Suggestions? 

I think this could be of use for trolling to have a forward view.

Pool noodles bro

Why not go with a manually operated mount made from PVC or something.

Or an old cop car spotlight. Like an Appleton or similar. 360° rotation plus up and down!

Do you have a Hobie? Might be able to exploit the pedal motion somehow?

oscillating fan motor somehow?

oscillating fan motor somehow?

Perfect . I'll pick up a cheap one and it should have what I need. Front scan, sidescan, structure scan and chirp. I think I have it all covered.