Very lightweight buggy?

I am looking to buy a very lightweight buggy for my 8 month old boy. I have a buggy already but it's impossible to manage when I have to take him on a bus. I have no problem putting it up and down but can't pick it up whilst holding my baby to get on the bus or pick it up again to get off! Someone else has to help me do it - and there isn't always someone nice on the bus who offers! So I need one which is really lightweight. Doesn't matter about all the extras as is literraly for going a few stops on a bus to my mums house. Any suggestions? Thank you :)