We've got one of these and they are brill, although not really suitable for such a young baby yet. http://www.handysitt.dk/page3.asp
We found that our son needed a proper high-chair (tripp-trapp or similar) until he was, perhaps, 8 or 9 months old when he was a bit more stable.
But the Handysitt is great for taking to restaurants because it fits most chair-types.
I realise you have put this in the "Wanted" section but just thought I would give you the idea of this chair anyway.