"He who marches out of step hears another drum." ~ Ken Kesey
I can get close drawing a shape, applying a gradient and running through RasterBator.http://arje.net/rasterbatorRasterbator is most often used to make really really big multi pages from a small drawing for putting up on walls, but can be set to size down to a single sheet when running.Oh, Rasterbator is a standalone that reads .jpgs, etc. and outputs to a .pdf that you can snap a pic from and turn to any format needed.
Check vectorious.net also.... I know they had a tone of these half tone style elements. I will look at all the ones I have saved later. I use them behind designs all the time.
I traditionally use the ones down in grayscale, converted to bitmap, then halftone. The trick to getting really good (large dots) is to use a very high, extremely high rez and a small size. Say, 1200 ppi gradation at 2" x 2" and convert to a 2 lpi halftone. Then, re-size the grayscale to 4 times that size with the re-sample (un checked). That will resize your resolution down but keep a clean image. Then, drop that into Illustrator and convert to vector art.To add to the effects, you can distort that vector gradation in your vector program.
Check out Fluid designs he was working some neat bending halftone effects a while back, I think he mentioned a tut on it but not sure. I know a way of doing something like on the can but it is an extreme PITA requiring blends along paths etc. not worth getting into at all, I would be interested in hearing what Richard figured out, judging by one of his pieces he had it down pat.