Tom, do you just plug the capacitor into the battery holder, soldering the leads to the +/- terminal? Thats a great idea. As nahuelmarisi points out, I use different disks with the Mac, so the only thing you really need it for is the clock. If I had a solution that would hold the settings for a week between startups, that's all I would really need.

So, Charlieman, the battery no longer seems to be sold by RadioShack either. It had been for years and I had assumed it was the environmentally free model as well since we have similar laws in the US – guess not. Evidently all the recent activity brought their attention to it and they removed it. Looks like we'll all have to use your UK source! LOL Thank you for posting it. But seriously, it doesn't seem that expensive for a battery that may well last 20 years as mine has. I assume that's one reason why Apple started putting them inside the Macs rather than making the user accessible. It also costs a manufacturer much more to make and stock a custom battery that does not have widespread use. Seems like a fair price to me under the circumstances, for the proper battery to fit properly in the Mac and won't poison the environment when disposed.

Here are several sources in the US discovered after a simple Google search (about $4 more than the RS price): http://www.lowcostbatteries.com/exell_px21-fslash-523_photo-batteries_95437_part_exell-px21-523.htm

http://www.welovemacs.com/bat3020.html

(Here for $7) http://www.batteriesinaflash.com/index.php?main_page=product_info&products_id=1546

http://item.express.ebay.com/Cameras-Photo_Film-Cameras-Film-Accessories_Film-Camera-Accessories_PX21-523-A133-A21-BATTERY-for-POLAROID-CAMERAS_W0QQitemZ7623076949QQihZ017QQptdnZFilmQ20CameraQ20AccessoriesQQddnZCamerasQ20Q26Q20PhotoQQadnZFilmQ20CamerasQ2cQ20FilmQ20Q26Q20AccessoriesQQptdiZ576QQddiZ1358QQadiZ1350QQcmdZExpressItem

($10) http://store.batteryspecialists.com/a21px.html