Well, I (personally) think your best options are to either make your own linkage or I can send you a laser cut linkage kit tomorrow! (but you’d have to pay for it 
)
Here’s a direct link to the linkage kit on Etsy. And more information can be found at the top of this thread: Linkage kits are now available! 🎉
Or perhaps you have another crazy idea of how to solve the quadrilateral kinematics problem? We like crazy ideas around here!