Smallest Navionics enabled depthfinder?

[billmac]

What is the smallest (translation: least expensive) Navionics enabled depthfinder?  It was borne in on me yesterday on the St. Lawrence, that if I want to follow contours effectively, I need a depthfinder on my bow.  I had planned to put an inexpensive Garmin Striker 4 up there, but that wouldn't really help me.  

[TnRiver46]

I’ve got mapping on my Lowrance elite 4HDI. It’s not super precise but close, you can always follow contours just by watching depth 

[JimT]

I think maybe the smallest Garmin echomap unit does? it's a 4" screen and is in the $300-$350 range 

[billmac]

I'm actually thinking of using the Navionics app with a tablet as an alternative.

[TnRiver46]

I forgot to add my unit pictured above was 200 bucks 6-7 years ago