Just looking to get the standard 2d sonar? If so any lowrance will work. The 2d sonar is all the same adapters up to the new HDS Live, I believe. The Boat Center here in Ramsey MN has several head units of Lowrance that are discounted very nicely. Feel free to give our parts department a call at 763-450-0400
If you have more questions feel free to contact me at the same number.
The 2D (HST-WSBL Transducer from the HDS Gen 1) is fine all the way up through HDS Carbon units, but technically the new HDS Live units as well. You just need the 9 to 7 pin adapter cable (7 pin to 9 pin adapter cable) which is pretty cheap to make it work.
Thats what I did with my old ducer to my new Live units.