Hi, I am looking for a quad doggie wheelchair for my 3 year old 7.8 pound chihuahua. She lost movement in 3 of her legs 2 weeks ago and no one knows why. If anyone can get me one cheap, free, or get me instructions to build one, that would be awesome! I have looked EVERYWHERE online and they start at $400, which is way too much for a single girl to afford! My Jeannie is such an angel and she has so much love yet to give I don't want to have her put down! Please, any help is appreciated! Thank you!

Here are a few links I found. Hopefully at least one is helpful.

It looks like you would have to modify a two-wheeled set-up, but it shouldn't be that hard. Add extra straps to turn the harness into a sling. Add an extra support bar in the front, and another set of wheels.

DIY Dog Wheels

How to Build a Doggie Wheelchair | eHow.com

Dog Wheelchairs

Wheels For Dogs - Homemade Dog Cart Ideas and Plans