If this method had already been posted then I apoligize
I was going thru auctiva and I noticed the default winning bidder template(e-mail automatically sent to your winning bidder)..You could change it to have your own custom "Buy Buttons" from Google Checkout and PayPal.
That way eBay and PayPal arent sharing information and you still can accept PayPal and Google Checkout.
Lol..i would be kinda mad if after all that they put the item # in the notes section..but if cart manager is that cheap then it would be a better alternative anyways..