If all you want to do is a few holes in timber, and not too worried about the accuracy of the diameter, you can knock up your own bit from a length of mild steel rod.
I have a six foot long job that I made and have used succesfully on many occasions (well about half a dozen anyway). Starting with the round rod, I heated up the end with a blow torch untill it was glowing bright orange. Hammered the end to form a flat wide section Filed the end to form two flat edges meeting in the middle at an angle of about 120 degrees. Paying attention to the edges, filed these so that they have a clearance angle of about 5 degrees. Finally heated the worked area up as hot as I could get it, and quenched it in a pot of used Chip fat (Vegetable Oil). It goes through structural timber like a dose of salts.