Hello again - so glad the stroller has been custom fit for you! I had wondered if a product we beta-tested might work for you. It's called a "KIDSERT" and you can use it as an insert for an umbrella stroller. Our son with CP was one of the first testers years ago. It was developed with the pediatric rehab hospital that follows our son here in Toronto.
Eek! I just checked it out and I've seen retail prices from $80-141 US (and more expensive here in Canada). No wonder the family we gave ours to was so happy...
Have a great trip!