I made a fair-sized batch of these so a client could finish up his run of custom markers, and since I had the machine set up, I cranked out a fistful or two for myself as well.
They're hand-polished one-piece stainless with a Delrin ball. I'm asking $14 each and shipping will be  $2 (for up to about eight at a time) anywhere in the US. For Canada and overseas, email me for a shipping quote.
My PayPal is email@example.com
and I'll get one (or more) heading your way! Update, August 20:
I have several hundred in stock and ready to go. I've been sending them out in padded envelopes using First Class, so shipping for any amount up to about eight is now just $2. That means if you order one, it's just $16 shipped, anywhere in the US!