I purchased a hummingbird DI 788 series......works GREAT. Has built in lakefinder maps, which are not too bad, but I upgraded to Navionics East chipset.
I purchased the unit for 699 from a cousin that runs a shop......good shop, and I think that deal is still available, but I bet you can find that finder for that price or better now.
The mapchip was another 150 bucks though
Later,
Geo