We have a Kelty Carrier in good condition (looks used, works) that our 4 year old has grown out of.

It features:
4 wheels
sunroof attachment with viewer and screen
zip on and off pack for rear
fully adjustable seat height

secure shoulder strap harness is fully adjustable
has a bottom carrier in stroller mode
easy to use
comfortable to carry
adjusts for size of adult carrying it

We went all over the Maritimes and Mexico with this wonderful device - no stroller or other carrying devices needed aside from a cloth sling. It is very stable to pick up and set down.

Originally cost @$300 with the sunroof accessory.
It's definitely used:
~ some fading of fabric
~ loose elastics on wheel covers
~ bottom frame repaired with dowels
~ brakes can be irritating to snap on

We are selling it for "Best Offer" preferably to someone who can pick it up using active transportation! We are at Ossington and College in Toronto.