M.H.
I don't know that this helps, but they make a t-strap that you can buy from amazon.com to attach your car seat to your carry-on. We have used it quite a bit and LOVE it. It means that we don't have to carry the car seat around, but we can still bring the stroller that we love as well. Here is the link for it:
http://www.amazon.com/Traveling-Toddler-Seat-Travel-Acces...
You could probably make something similar yourself if you are really looking to save money!