Can I make my own foil faced insulation?
Like @keshlam said, a quick search online will tell you what you need to know...

Seems like SilverGlo is a product designed by the Dr. Energy Saver company, which also was the company behind the video you saw. Apparently, this product is simply rigid foam board of the Expanded Polystyrene variety (EPS), covered with their radiant barrier facing. EPS actually has the lowest R-value of all the foam board types. 

See: Dr. Energy Saver Rigid Foam Wall Insulation

If you want something with higher R-value, try using one of the other foam board types, like polyisocyanurate or Extruded Polystyrene (XPS). Polyisocyanurate usually comes faced with foil on both sides. You can easily find both at big box stores in a variety of thicknesses. 

As for 3" thickness, they might not carry, but you can always stack and glue/mechanically fasten smaller thicknesses up to the thickness you require. 

I would also check local distributors/contractor oriented stores that sell to consumers. They may have better pricing and also delivery services. From personal experience, a 4ft by 8ft standard sheet of rigid foam board does not fit inside the small SUVs (RAV4/CRV etc) they make nowadays...