i did the same , Adam, knocking at the top of the PF.. until i got a knock box :)
it comes very natural to hit the bar with the middle of the PF.
the small one we have on the bench *certainly is dishwasher safe; we got it from Coffeeparts
( http://coffeeparts.com/accessories/tubes.html ): it is the mini benchtop version.
it holds just enough pucks to get me through the day, (about 6-7).