You can buy just the inserts, you know with the 1/4" hex on one end and the clutch on the other.

I bought a few at the local hardware store.

you can also get the bits from McMaster Carr.
http://www.mcmaster.com/

page 2755 in the online catalog, all 5 sizes for less than $6 total.

part numbers for the short ones:
7188A31
7188A21
7188A23
7188A24
7188A32

longer ones available, look at the page mentioned above.

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
---All pictures---
"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-