They do come up on ebay.UK from time to time, but not often due, I would guess, to the size and weight. The bowl weighs over 2K without the frog or statuette and I think I remember that the last complete set I saw stood about 8 inches high.
I bought my bowl at a local b&m outlet unfortunately without the centre-piece. It's a sort of turquoise/blue and if anyone has one or knows where there is one I would be very interested.
I hope I'm not breaking any rules by giving a mention to the outlet, I'm not involved with it apart from being a buyer. It's called The Emporium. It was originally an ice-skating rink and is now full of small trading stalls of collectables, loads of glass of various styles and periods.