PDA GPS power issues (i.trek Mouse)

Hello everyone.. I've posted this question in a few different NG's
and forums, so appologies in advance for anyone reading it again.

Anyow..

I have a Sony Clie TJ25 Palm-OS PDA that I recently purchased an
i.trek mouse GPS receiver for from Semsons & Co. in the USA. I'm
located in Canada, myself...if that matters.

Anyhow, I plan on using the GPS mainly for general-aviation navigation
as well as the odd Geocaching adventure.

However, I have discovered a problem - The i.trek unit will *not* work
unless the cigarette lighter power plug (Which is part of the PDA to
GPS interface cable) is plugged in. I didn't know this ahead of
time.

Now, this presents several problems:

First, when Geocaching, I'm obviously not near a 12v cigarette lighter
plug.

Secondly, not all of the rental aircraft that I fly are equipped with
cigarette lighter power sources. Additionally, most planes I fly
(Cessna's) are a 24v power system, and I'm unsure yet if the power
adapter that is part of the i.trek PDA interface cable will accept
this high of a voltage. I'd hate to fry the GPS itself, and the PDA,
finding out the hard way.

In a pinch, I can band-aid some sort of "portable" 12v power supply
using non-spillable batteries and some sort of backpack for
portability sake, but it starts to get cumbersome at that point.
Additionally, everyone here knows that every pound counts - carrying
around extra batteries to power a GPS isn't ideal. As it is, with
myself and another sturdy individual in a 152, we're already running
less then 3/4 tanks to stay within W&B. :-)

I know that other "direct" cables for mouse-style GPS units actually
power the GPS from the PDA (Which is what I desire), but I'm stuck
without that option apparently at this point.

I'm wondering if anyone else has run into this problem, and what the
solution might have been? Can I buy a PDA connector for my Sony from
eBay, and hack it into a direct cable successfully? Is there some
sort of modification possible to the cable I have now to enable
powering the GPS from the PDA even when it's not plugged into the
cigarette lighter?

I know that many mouse GPS units *can* be powered directly from the
PDA..but unfortunately mine doesn't appear to be one of them..yet.

I'm quite happy with the actual i.trek unit at this point, regardless
- it's been performing excellent to date, although I have not yet
taken it airborne.

Regarding batteries, the TJ25 has an *excellent* battery onboard, and
even with the GPS draw I would still except several hours of runtime -
fine for 90% of my flights.

Anyone have any "Been-there-done-that" stories, or solutions?

Any assistance appreciated!

Email me or respond here, either is great. Any emailers will need to
de-munge my antispammed email address first.

Thanks everyone!
Mark