Personally, I've had very good luck finding the correct legnth drive shaft out of of other cars. It may take a while going through the drive shaft pile or crawling under cars at a wrecking yard, but it has generally paid off.

On a few occasions I have taken a longer shaft and cut it down myself with good results.

First I try to find a shaft a few inches longer than is needed. I look for a shaft that does not have balance weights welded to it (by doing this I've never needed to have it sent in to be balanced afterwards). First I scribe a straight line on the yolk and the shaft past where it's going to be shortened. Then I carefully grind the weld that hold the yolk to the shaft. When you remove the yolk, you will find that it's usually a stepped plug that fits into the drive shaft tube. I then cut the shaft to legnth using a roller type pipe cutter (they look alike a giant tubing cutter that most of us have in our tool box) if your friends with a plumber he might let you borrow his. This gives you a square shoulder for the yolk to sit in.

Tap the yolk into the tube using the scribe line to insure it's indexed properly, and insure it's square. Tack weld in 4 even spaces and chect to insure it's still square, then final weld it into the tube.