Surely I tell how to determine the length of the bushing in the article. It's not a fixed length per se but a length that is suiteble for YOUR fore-end on YOUR rifle against YOUR trigger guard.
But to be honest, while you COULD machine one up from scratch, at what point do pennies become uneconomic? If you don't want to go to the expense of two original new trigger and sear axis pins, there's a cheaper way to go. Get ONE PIN, cap, fore-end and cut that into two lengths. One for the trigger axis and one for the sear axis pin. It is the exact diameter and that way, one long pin will get you two short pins.