This is very similar to the capper I use for my homebrew...
I've thought about converting it to a pen press, but I need to keep the bottle capping functionality, so I've stuck with my drill press as a pen press so far.
This one happens to be at a shop local to me, but I'm sure it's available anywhere homebrew supplies are sold. Or you could buy it online here...
[urlhttp://www.morebeer.com/product.html?product_id=15676[/url]
I didn't look for a better price, so it might be available cheaper elsewhere.