When I have questions like that (been there!) - I go to the manufacturer. They have never let me down TRUGLO included. They all know their hardware very well. (My experience)
You will also be amazed at the vast array of small machine screw hardware available on eBay and Amazon. They have all the goods that the local hardware stopped carrying (Fastenall included) years ago.
You MAY have to buy a large quantity to get the one that you want BUT the price will be wholesale and not highway / inter web robbery!!