I bought this one after seeing it mentioned earlier in thread
amazon.com/gp/product/B0064REJ3C
Tip is massive, pretty awkward to write/draw neatly, and the clip on it broke off within 24hours.
This popped up as a suggested buy when i was buying something earlier, so for $10 I threw it in for a look
amazon.com/gp/product/B006GM57MC
Hopefully it'll be a better buy given that its a fair bit slimmer...
For $10 this is the stylus you want:
http://www.amazon.com/Griffin-GC160...1?s=electronics&ie=UTF8&qid=1331835447&sr=1-1
It is far more responsive than the one you said broke, I have 3 of those (sold under the 'Cosmos' brand). It is also better than the Boxwave.
All of those bubble tip styli are about the same size, so if you found them to be too large for you to use comfortably you might wanna go with a Jot Classic:
http://www.amazon.com/Adonit-Classi...5?s=electronics&ie=UTF8&qid=1331835525&sr=1-5
The Griffin is great for loose sketching & digital painting. It can also be used to write if you write large (which you have to on the Prime). The Jot is just as responsive, but has a finer and slightly more accurate tip. Also just because of the way the Jot is built you will find yourself writing and drawing slower with it.
These two are my "go-to" styli for use with the Prime, or any other touchscreen device.
P.S. don't go with the Jot Pro unless you think a rubber grip is worth the extra $10. The magnet that holds it onto the iPad doesn't work with the Prime