i did the same thing
I have a 2002 LX. I bought a 2003.5 msp spoiler off ebay for about $300. Set up a paint booth in the garage and painted for around $40. Measured where to put it 500 times, bit my tongue then drilled the holes. Looks great.
The only problem is minor, which is that I got one with a light in it, when I hit the breaks, not all the lights turn on at the same time, one tail light turns on a split second after the rest. It could just be my car, either way it doesnt bother me..
By the way... don't order from spoilerdepot.com.... I did that first and they didn't have them in stock.... and it took forever to communicate.... just a heads up.