Really stinks that they sold the bed after telling you they'd hold it
I thought Little Tykes used to make an airplane bed but I can only find references to race car beds.
Would really nice airplane bedding suffice? Found lots of adorable designs here:
http://www.squidoo.com/airplanebedding
Lots of great accessories at the bottom of that link as well
The only other thing I can think is to find someone who is a good woodworker and ask them to make one for you. That could run you $1000 as well but you could make it exactly to your specs.
Good luck!