To my knowledge no one makes a handheld
GPS that uses free NOAA
charts. All Garmins use their own proprietary charts, and the few other brands I've seen seem to use some variation on CMAP or
Navionics.
One option is to use an
iPhone with
iNavX, which supports NOAA raster (but not vector) charts. There are a variety of threads around about the
iPhone and options for waterproofing.
Another is to find a weatherproof tablet PC, or use a netbook or similar down below hooked to a weatherproof
monitor on-deck. On either you could use
OpenCPN which supports both NOAA
ENC and raster charts.
None of that is very satisfying, I know, but that's the state of things. Most GPS manufacturers appear to be doing everything they can to keep you locked into pay-charts.