go in "files" area an d look for UPS-5V.rar
it is an italian forum where someone posted a 5V ups fou slug, easy to
fai-da-te make-on-your-own !! I'm just forward this.
it can be also useful, if you are planning to roll out an outside
walking whith a battery powered slug (just add batteries in series).
it is for european 215/230V but i think would be re-ingeneered to work
with other nation's voltage. (usa, canada, japan and so on).
HTH and also visit our italian forum, NSLU2 rocks all-over the world !!!