Cut off a reamer of the right taper to the size you need.... but as much as they're getting for even the most basic fiddle-peg reamers now, I wouldn't want to do that for just one job.
One thing I've done is to taper a piece of dowel with my peg shaver, and glue 3 or 4 skinny little strips of sandpaper along that. Chuck the dowel in an electric drill and run it real slow... Yes, the sandpaper wears out almost immediately, but if I've got the hole almost right before I start (drilled in steps of 1/32" or so), I might only have to change it once before I've got a smooth, correctly-tapered hole.
OR.... You can get a nice reamer real cheap at Harbor Freight (I suspect the StewMac is a similar one that's been shortened), and cut it wherever you want with a Dremel cutoff wheel. They're about twice as steep a taper as a normal violin peg, but it would be easy enough make a tool make your peg match that-- This video drives me nuts with the camera jumping around, but the idea is genius, and it does work:youtube.com/watch?v=Kt75XRPvimU
I've only done it a couple of times, but what works for me has been to take a drill bit, sized depending on the peg size, and drill the hole, and then while keeping the drill running I make a sort of circular waggle with the arm that holds the drill, so that the sides of the drill bit are shaving away a tiny bit of wood. I check the fit after each repeat of the waggle, and when it's getting close I cut a small piece of 150 grit or so PSA sandpaper and stick it to the peg and give it a few turns around to refine the fit. I would practice the waggle on scrap wood first, it's not hard to do but hard to describe. It's also probably not a proper thing to do, but it does get the job done. It's much nicer to be able to use a reamer, I'm sure, and if I had to do it at all often I would get another one and cut it off. I have a Stew-Mac reamer and a peg shaver that I got off eBay, and I enjoy using them for fiddles, and banjo pegheads. Zach
If you're going to use actual wooden violin pegs it's imperative that the fit is correct, otherwise they will be difficult to tune and won't hold tension. The reamer at the right of the photo was made by cutting off a standard violin peg reamer to the appropriate length.
Violin pegs that have been properly fitted aren't difficult to tune accurately if synthetic strings are used. (Steel strings and wooden friction pegs are NOT a good pairing...).
This is one case where there isn't a good substitute for a proper reamer. All the other home brew tools won't produce the kind of fit that it takes for a wooden peg to perform at its best. (I think I've tried all the alternative methods... ) Proper violin reamers can be found on Ebay. I've seen the lower-tier reamers for less than $20. The higher quality reamers are usually triple that price. International Violin occasionally runs good sale prices on reamers, too.
The general purpose hardware store reamer has a much steeper rate of taper and pegs that are fitted to that angle will have difficulty with holding tension.
A peg shaver (the other half of what it takes to have well-fitting pegs) can be shop-made, but the reamer is the more important tool. There's a shot of my shop made peg shaver in my home page photos. It is made by drilling a hole in a small section of hardwood block, using the reamer to produce a tapered hole, then carefully cutting a matching slot along the conical hole and clamping a sharp planer blade over the slot. You end up with a giant version of the pencil sharpener we all used in grade school.