Fllight Recorder Wars, Part II: What Backup to Use?

I'm currently using a Cambridge LNAV, a GPS/NAV model 20, and Pocket
NAV on a Compaq 1530. Last summer, I experienced my first flight
recorder hardware failure just before (thank goodness) a contest. So
I am looking at backup options. I'd like an add-on device; I have
neither the money nor the inclination for a complete
vario/computer/flight recorder transplant.

I've heard the arguments for/against various brands, technical
approaches, etc., for a primary flight recorder. I'm interested in
knowing what makes sense for a BACKUP GPS flight recorder that will:

1) act as a "dumb logger" (i.e., connect it to a separate battery,
switch on, and forget) for backup purposes

2) in the event of a failure of the primary flight recorder, could IN
FLIGHT be connected to my LNAV and/or Pocket NAV/Compaq WITHOUT
compromising the integrity of the record in the backup recorder. This
could involve swapping cables from one device to another (my current
GPS/NAV is accessible in the cockpit now) or making up a special "Y"
connector and/or switch.

I drove my LNAV with an early Magellan "fish finder" GPS receiver for
years before I bought the Cambridge flight recorder so I'm not averse
to carrying an independent backup flight recorder PLUS a cheap
handheld that could be powered up to provide GPS info to the LNAV
and/or PocketNAV for navigation.

Regarding navigation, I'm old fashioned enough that I can (and still
do) use a map. But today's start and finish cylinders, turn-area
tasks, stiff penalties for restricted airspace encroachment, and tight
final glides seem to demand some sort of moving map nav display.

Those of you who remember my tirades against manadatory flight
recorders years ago (despite assurances of their reliability) will
appreciate the irony of my predicament, as well as my reaction last
summer to (1) the technician's comment that he'd never seen my failure
mode before, and (2) the $350 repair bill.

My primary application is U.S. regional and national contests.

Will consider new or used. Thanks for any suggestions.

Chip Bearden