I believe he's referring to the front sight pins installed on M1917 rifles by the Danishicon. They should be a standard size of either English/American or Metric.
They are spring pins or sometimes incorrectly referred to as roll pins. Most industrial suppliers should have them such as Granger, MSC Supply and Fastenal. Your best bet is to go to a location with the pin or the sight base if it's missing so they can take a measurement to match it up. Odds are the replacement pin won't be the exactly correct length so it will need to be cut with a hacksaw or ground down with whatever method is available. Getting the pin height to a correct length can sight the rifle in to as close as 25 yards.