I love my Humminbird 160 Portable. Bought it as Bass Pro for like $140. Looked and it may be this is the current model: https://www.basspro.com/Humminbird-PiranhaMax-175-PT-Fishfinder/product/1211081052/
I have a canoe, a jon boat and my deep V and this goes from one to another very well. It has it's own battery, I'm sure if you wanted to rig it up to a battery of your own you could get cheaper. But this thing has it's own protective bag, a suction cup transducer with a very long cord- it's all nicely contained. The battery lasts for a very, very long time. I really only need to charge it a half dozen times a year and it gets used a lot. Simple but effective. Shows water temp which is nice if you fish coldwater species at all. One thing I like about Humminbird as opposed to other brands (which could very well have changed since I bought) is that you can zoom in on anywhere in the water column. Most entry level sonars will only zoom on the bottom but say you are chasing crappie, which tend to stay higher in the water column than other species. You find that you are in 25' of water but are marking most of the crappie at 10 feet. You can zoom in on the 6-12' portion of water. One last thing I can say about Humminbird is that their customer service is exceptional. I use a high end flasher of thiers when I ice fish and had troubles with it well after the warranty period. They still had me send it in and I waited for a phone call asking for payment to fix the unit, but within 4 days I had my ice sonar back, fixed, good as new. Great company to deal with.