A true suckling pig is usually quite small. Often what gets referred to as suckling pigs are just young pigs. But to truly be a suckling means it still feeding off the mother's milk. Apparently this makes them taste different than expected. I think they "technically" max out around 10 or 12 pounds if I recall. I read somewhere that finding them is tricky as there is no profit in it for a farmer, butcher etc.
I also recall reading (pretty sure it was on this site) that the the 26" kettle was basically designed around a suckling pig; so it should definitely fit!