"Decent" and "under $200" might be something of a misnomer so I'm going to suggest something that costs a little more.
This is my Garmin Striker 5cv, so called because it is 5 inches across, which is the right size (in my view) for a kayak, not too big and unwieldy, but not too small to see.
It comes in a pack with a transducer and is around $300. However I suggested it because for $200 you will get only get something a lot less desirable. Has most features you would expect in a cheap end fish finder, just, doesn't have maps, although that is a non issue for where I fish.
Runs all day on a 12 volt 7 amp hour battery you have to buy separately, these can be purchased for 30 or 40 bucks although a high quality one costs more but is worth it in my view.
Here's a link to an ad for one https://www.amazon.com/Garmin-Transduce ... 865Z4?th=1
Here's a pic of mine
