There is a new pilot cutter replica which I am told does skippered charters out of Oban I would be surprised if they do not do the Malts cruise. I have no contact details, but the boat is called Mischief and is a replica of Tilman's yacht of that name. Beautiful boat, built in a Welsh yard about two years ago I see it from time to time in the Crinan canal. Another possiblity is 'Edna Frantzen'? (I may have spelt the name wrong) she is based at Doune, just north of Loch Nevis and you see her in these waters all the time. You might get info. on www.doune-knoydart.co.uk.
However this event is popular and usually oversubscribed so berths on these desirable craft are probably booked a year ahead.
Strongly recommend that you try Lizzie May. I declare an interest, having been invited on board for a cup of tea at Largs. Brilliant looking boat that I am sure will look after her crew. According to her on line sailing programme she is doing the Crinnan Classics and then the Classic Malts Cruise: