Kensington fan here but I have an iBook, and iPod.
http://www.us.kensington.comI have the big AC/DC version for when I'm away in hotels, and a really small light DC version for the Aircraft. That way I don't fill my lugguage up with PSU's.
You can get tips for mobiles, PDA's etc ...
Look on eBay.com (Not UK) there's loads on there, and much cheaper than the UK stores.
Or if you're visiting the US, Circuit City have them as stock items as well as the brand Decker mentioned.
Having said that I brought the small Kensington charger and tips in Dixons at Gatwick's North Terminal on special offer lat year for £29.95. RRP £65