I have used the plastic trim from car model kits ( shaved down to the right diameter) and inserted the plastic into the holes were the nylon was removed or lost due to rebuilding the shaft.
Since the original pins were made of plastic ( never knew what type of plastic) I simply used an alternative plastic that I found at home.
How I did it;
1. Take some leftover plastic from a model car/airplane kit. I used the tubular frame work that holds the plastic parts for the model kit. It is much easier to work with a 2-3 inch section of this while you file the plastic down the correct diameter.
2. Using a model kit file ( 1/4 inch wide), I slowly filed the plastic down until it was a snug fit into the guide pin hole on the steering column shaft. I made this section about 1 1/4 inch long. Remember I needed multiple replacement plastic pins.
3. Once the correct diameter was achieved I cut off 3/8 inch long sections for each pin hole on the steering column.
4. Align up the pin guide hole, insert a small amount of glue on the replacement pins and insert into the pin guideline hole on the steering shaft. I used a pair of needle-nose pliers to hold & insert the replacement pin. A super glue sold to body shops ( about the same as any super glue sold in stores) was used. I don’t think it really matters what type of glue as long as it holds up. I could see hot glue working just as well.
Since the pins are there to hold the steering column shaft in place until the time of a collision, I don't think the type of plastic is really all that important. The force of an impact that hits the car hard enough to move the frame rails, steering box, etc.. that would force the steering column to collapse will not have an impact of the type of plastic used for the pins.
Alternative methods that I have seen;
1. Wood dowels used as pins. The type you see at home centers or wood working shops. Again consider the force of impact to bend metal and I believe even wood dowels ( as small as the dowel used for the pin replacement on the steering column) would work as well.
2. Use a plastic welder, the type used by body shops and melt one of the plastic repair rods into the pin guide holes
3. Soft metal rods (similiar to welding rods, super soft). This was seen on a street rod I worked on. The owner had another shop repair the steering shaft and inserted the metal rod. Again, the thought behind the owner, the metal was soft enough to shear if the car was hit that hard. I personally wanted plastic on my own cars, but to each his own.
It all depends on how close to original you want to go and how you feel about the strength of the replacement pin used on the steering column. If you wanted to complete some research you could consider what they call the "shear" or "tear" strenght of the original plastic pin on the car and find an alternative material to find the "shear" or "tear" strenght to match up as close as possible. Although the force of an impact to the car to move a steering column is great which means almost any soft material close to the strenght as the orginal, be it plastic, wood or metal would work closely the same way.