How to build a combination hand & foot cycle My two-year-old daughter has a full right arm, a left arm that stops above where her elbow would be, no right leg at all, and a full left leg. We have found a product she can ride (the Amtryke), but it's awfully expensive.

The goal is to have a hand and foot cycle that is something like this product:  http://www.amtrykestore.org/AM-9XS_AM-9S-AM-9S_with_Bucket_Seat.html

We don't want to purchase that product due to cost... we are willing to build it ourselves in order to keep the cost down. Maybe we could collect parts from multiple used kids' tricycles? 

We would be willing to purchase a bike if it were more in the $100 range - - the above product would be $400 for now, and she'd grow out of that quickly and need the $700 version. That's WAY too expensive for us!
I think you can probably get a copy of the PET plans for free, if you ask nice.  It's a pure handcycle, but designed for easy construction, and they should have sources for the parts, etc.  You could perhaps adapt the design for your needs.