If you are looking for an SSC (soft structured carrier) like an Ergo - the Kanga XT is a great toddler-preschooler carrier (google Bloo Kangaroo), but not easy to get hold of, as is the Kinderpack. I use my full sized Beetlebums and Bamberoo for my 3 year old (who is about 16kg but very tall, he's in a EI class with four and five year olds and is taller than all of them) - and he is good height wise with arms out.

Or, there are some very supportive woven wraps which are great for larger kids. BBSlen wraps are great for toddlers because they are super wide, and they are bomb proof so you don't have to baby them like some other really supportive wraps. Storchenwiege wraps are also good, but not as wide.