To cut through the fog of ignorance....
- All oem Raymarine, B&G, Lowrance, and Simrad transducers are made by Airmar.
- 80% plus of Garmin, Humminbird, and Furuno oem transducers are also made by Airmar.
- Of American-made fishfinders, only Humminbird and Furuno make some of their their own transducers, and then only for some smaller or commercial sonar units.
- Garmin, Si-tex and Furuno all also buy a small number of transducers from Nantong Saiyang Electronics of Jiangsu, China.
- Furuno also sources commercial 'ducers from Kongsberg Maritime of Kongsberg, Norway
- Saiyang and Kongsberg transducers can be purchased for most of the above companies' machines, but you may have to get the appropriate connector and connect the pin-outs yourself
Also, a MFD with CHiRP technology is much less expensive than you think.
A Raymarine a68 5" MFD with touchscreen, Wi-fi, and including a CHiRP capable CT100 transom-mount transducer is under $1090 complete from West Marine. Add in the Navionics Gold 2D chart for $190, and you're at $1280 plus tax on the whole bundle, and it's pretty sweet.
__________________
Common Sense is learning from your mistakes. Wisdom is learning from the other guy's mistakes.
Fr. Frank says:
Jesus liked fishing, too. He even walked on water to get to the boat!
Currently without a SeaCraft 
(2) Pompano 12' fishing kayaks
'73 Cobia 18' prototype "Casting Skiff", 70hp Mercury