Gas Cap On Lime Green Truck in Truckin???

[muddpile]

I just bought the new issue of Truckin (Vol. 31 No. 4 2005) and on page 223-225, there is a lime green 67 short steppie with a really nice flush mount aluminum gas cap in the factory location. I have not decided whether or not I am going to do the blazer tank, so if I don't, I want to use this gas cap. I have seen them before and they thread off with a special tool. I have no idea how you mount them to the original tank, or where I saw them for sale. Does anyone know where I can get one and how I can mount it? Thanks!