Here in Australia, there aren't to many places in the bush where you would be able to use a baby stroller and still get to the places you really want to photograph, so I have to use a backpack. This is what I did.
I made a polystyrene foam insert for my Black Wolf backack and then covered the foam with a tough yet soft fabric. The pack is still fairly light and all of my 8x10 gear is protected. All you need for the insert is some 1 inch thick foam for the outside and base and 1/2 inch for the interior, and then use PVA glue to stick it all together. Let it cure for a day cover it with the fabric using more glue and Bob's your uncle. Done. Just make sure you get your measurements for all your gear right first.
Mike