It's a dilemma that we've all faced: you need to take a bath, but you need to get somewhere at the same time. eBay seller toymaker46 offers this solution. He notes that it's not yet fully operational, so you'll have to work on it some.
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=150572093742&fromMakeTrack=true&ssPageName=VIP:watchlink:top:en#v4-37 via Jalopnik
http://www.bathtubbing.com/gallery.php