A year ago I was gifted a MIR Vest and I have to say, it's damn awesome. It's main advantage is that it stays on your upper chest, allowing you to perform high speed activities (run/jump) without it wobbling around and feeling awkward. If you have the money, something like it would be a good investment.

Mine is something like this: http://www.amazon.com/MiR-Adjustable-Weighted-WEIGHTS-INCLUDED/dp/B002E0S5I8/ref=sr_1_23?s=exercise-and-fitness&ie=UTF8&qid=1313759890&sr=1-23

Just find one that doesn't include the weights as that is what is adding so much cost. Making your own weights is easy and way cheaper.