The two stars have autographed their space suits, which cost a massive $30,000 each, and rock matriarch Sharon insists it's a must-have for any Bieber fan - because the teen's costume still smells of his sweat.
Showing off the outfits on her daytime show The Talk, she says, "These outfits cost $30,000 each. Justin was sweating all day, so it's covered in his sweat.
"They are unbelievable outfits... They're signed by the guys and it smells just like Justin! The money goes to a great, great cause."
All proceeds from the upcoming eBay sale will benefit the Sharon Osbourne Colon Cancer Program at Cedars-Sinai Medical Center in Los Angeles.
In the hilarious ad, Bieber doubled up as himself and a bearded soundman.