Bayraider.tv has dug up a nice find on eBay. It's an original R2-D2 dome!

"Well, apparently it's called a 'hero dome' if you use the proper lingo, but anyway. It was worn by actor Kenny Baker for Star Wars: Return of the Jedi and also for The Phantom Menace, and still has the original fibre optics inside, along with the original holoeyes (which were apparently filched from a Vickers passenger jet).

The dome was replaced when it got too difficult to rotate ? it is getting on a bit now after all ? and bizarrely was all set to be scrapped until an Elstree Studios employee rescued it. It was used in numerous close-ups in the two films, and comes with a letter from Kenny, who thinks he may have used it in The Empire Strikes Back, but can't be sure. The starting price is a whopping $100,000."

You can check out the auction right here. And before anyone asks, no I will not be bidding on this item for my ever growing R2-D2 focus collection!