If you're adventurous enough...
http://www.pipemakers.org/lucite03.html
Lucite Stem #491 is my favourite for using with cobs.
These are already drilled at 1/16", so you have a good straight hole to follow for your preferred draft size.
It's best to track down some tapered tip drill bits, they do work better for enlarging an existing hole when you're just using a handheld electric drill.
Anything with the 5/16" tenon will almost fit a filter stem cob out of the box, they just need a few minutes of sanding on the tenon.
If you're a handyman, at $5 a shot I think it's a good deal. The only place I can find locally to buy acrylic blocks basically sells them for the same price as these pre-shaped stems.
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