Go to your nearest bass pro, cabelas, or other sports store and look at all you have to choose from.
What you get really depends on what you plan to do. If you only need depth, a $79-$99 unit from Walmart will work fine, as long as you install the transducer properly, according to the instructions. Mount it wrong, and you won't read depth when moving at speed.
This Lowrance 5" is a great starter unit for $100. This is what I would buy for simple depth and fishing:
Lowrance Hook Reveal 5x Portable Fishfinder Splitshot with Down Scan Imaging
Move up to the $99-$129 range, and you should be able to get one with GPS plotting. The Garmin Striker4 and the Lowrance Hook2 work well for the money.
Here is a refurb unit for less than $100:
Here is a regular, new unit, $129:
Then of course, you can move up in features and $$$ up into the thousands of dollars, if desired. A VERY popular unit is the Garmin Echomap 93SV or 94SV. Full charts with contours, down scanning, side scanning and more. This is what I finally moved up to when on sale for $599 and I love it. I found a used Livescope system locally and that thing is amazing. As everyone says, it's a game changer
Unfortunately, you just missed all the black friday deals, but hopefully, you find something that works well for you