GPS accuracy under tree canopy

Dear list people:

I need a low end gps unit (under $1,000.00) that can consistantly
record waypoints within 10 meters of their actual location.  Here's
the catch:  the plots will be taken under tree canopy in Lousiana
(USA).  I've explored Garmin & Magellan & am looking at Lowrance as
well.

Thanks in advance,

Pete