You could try furniture.ie for a list of cabinet makers who could do this. A carpenter should also be able to do it but it may be a little rougher.
You could use brackets to support the table, these can be got in various strengths although the heavy duty ones are quite expensive. The heavy duty ones might otherwise be used for fold down seats in railway stations for example.
I think you should consider a 'gate leg' table I think they're called, possibly backed up by light duty brackets... the brackets would hold up the table top while you fold the gate legs against the wall, then you'd slightly lift the table top to release the brackets, the table top would then fold down to cover the legs... it should be nice and neat.
A carpenter may be able to do something a little cheaper and rougher as opposed to a cabinet maker who may be able to do something a little nicer but then it may cost a little bit more. You could make it yourself if you have access to a few tools.
Cheers
Joe