IPAQ to GPS Power Problems

Hi Forumites,

Old Bushie in post 27273 put me onto Jonny Appleseed GPS to get a cable that linked my IPAC 5450 to my Etrex Camo.

Now my problem is the power supply. The cable puts out 5 volts which is fine for the IPAQ but is too high for the Etrex (Johnny Appleseed did warn me about this, the older etrex's are OK). Is there some way I can tap into the cord that runs to the GPS to drop the voltage, (ie splice in some resistors or something?) I could splice the powersupply from another power cable for the GPS but then I need two 12 V outlets and there will be cables everywhere!

My schoolboy electronics is too long ago to remember the theory.

Thanks

Paj