I know all you are asking yourself if there are such thing and where can you find this Fish Finders? To make it easy for you I have compiled the list of Fish Finders that I found impressive but will not hurt your budget.
FFW-718
If you want something handy yet has a very promising features then this is a good choice! Can be used for both fresh and salt water, flawlessly detect and displays big, small fish or groups of big and small fish. Aside from that there is no hassle of getting your lines being tangle since it uses wireless sensor to transmit data. Very nice features for only USD69.50 (actually a good offer!). To check the other specs of this item you may click the link below.
FFW-718
http://www.gainexpress.com/collections/fish-finder/products/wireless-40m-fish-finder-sonar-sensor-dot-matrix-bottom-contour
FF-718LiW
If you are a fishing enthusiast you know how important the operational range is; wide operational range equates to a wider scope of area to fish with. One of the advantage of this Fish Finder is that the wireless operational range is 180m, just imagine how far you can go with this Fish Finder. It's equipped with Adjustable FSTN LCD screen that can Zoom at specified depth, for magnifying the area around the bottom revealing fish and structure close to the bottom that may not be visible in typical operation. Plus it floats in the water! Get this item for only USD129.90!
FF-718LiW:
http://www.gainexpress.com/collections/fish-finder/products/rechargeable-battery-wireless-fish-finder-0-6-40m-sensor
FF-718Li
A versatile Fish finder that make use of both wired transducer and wireless sensor. You can view fish icon & water depth, gives live update of bottom contour, water temperature in °C/°F, auto & manual range and wide area coverage of 100m (320ft) for transducer mode and 0.6~40m (2~131ft) for wireless mode. Promising item for only USD152.90!
FF-718Li:
http://www.gainexpress.com/collections/fish-finder/products/2in1-wireless-fishfinder-sensor-40m-wired-sonar-transducer-100m