Glad to help.
Aside from the tire irons/bead tools and the well made strap wrench, that should not be a hard set to mimick.
I have a bunch of the Griot Garage red nylon tool rolls I bought way back when and they are great. Too bad they stopped making them. Or really, carrying them. The roll will be another tough find although most boat shops or boat cover makers/sewing shops will happily make what you need I have found.
As for used sets, Griot's was the only vendor to carry USAG back in the mid to late 90's, and even today USAG tools are not well supported here in North America. I doubt at $500 a set they sold many.

Finding used is gonna be damn near impossible.
Good stuff and the Facom sets were priced similarly.
Most vehicle owners who wanted a tool set for teh trunk went to Sears. For $500 you could have put that 68-72 piece USAG set together for 3 or 4 cars with Sears tools.
USAG still makes kits, you just need to find out what works. And get it shipped.
http://www.usag-tools.com/catalog/en/products/families/146/tools_kits
Frenotec is the North American Distributor so you will have to go thru them unless you have a shipper in the EU.
http://www.frenotec.com/catalog/