Maybe the oStylus?
I have a big rubber tipped stylus and a ten one spongy tipped stylus, and I'm not happy with either. I would like to try the ostylus. Engadget said the biggest flaw is you have to be pretty accurate with the 'o', but if you drawing or something, it may be better than a sponge.
Engadget Review: engadget.com/2010/10/01/ostylus-capacitive-pen-review/
If anyone has one, I'd love to hear what you thought of it on a tablet.
As for trying to get a more pen like one, the wacom one is not the best, but it may be the best compromise. I suppose the hardest part is to get the amount of capacitance needed within the rubber or close enough to the screen for it to work.
Wacom stylus: engadget.com/2011/04/18/wacom-announces-capacitive-stylus-to-replace-puny-human-fingers/