We learned on vacation why the inflatable Baby Spa Bath by Go Home could be useful. At the time he'd never been in a full-sized tub and wasn't willing at the hotel. The Baby Spa Bath would have been a great way to keep him comfortable while remaining portable for travel.
The Baby Spa Bath has four suction cups on the underside for added stability and the bottom of the tub has ribbed sections so baby won't slip. It's available here for AUD$39.95.