There are several sources for superior quality American made files.
eBay under these categories:
Collectibles / Tools, Hardware & Locks / Tools / several subcategories
Home & Garden / Tools / Hand Tools / Files
Home & Garden / Tools / Hand Tools / Other
Business & Industrial / Manufacturing & Metalworking / Metalworking Tooling
When buying on eBay it is important to look at every possible listing regardless of how vague the description or how poor the pictures. Poor pictures and title can mean a bargain for you, but read the description. When in doubt about whether they are USA-made files, message the seller.
Flea markets are the cheapest source for USA files. Here they go for $1 each, maybe $2, regardless of size. Last summer I got an 18" mill bastard along with several other large files and the seller was surprised anyone was buying them. Try finding an 18" file anywhere.
Digging for Metal: How To Find Used and Vintage Tools at Flea Markets
Independent hardware stores with old stock
Internet forums with classified sections; there are many of these dealing with guns, edge tools, woodworking, machinists, and old machinery.
Craigslist, estate sales, auctions; anyplace there's a toolbox there are probably files.
Comparisons of American-made files versus other files:
Paul Sellers - Nicholson Files and Home Depot Blow It Again
Woodnet Forums - Test of Taper Saw Files
Tools for Working Wood - We Discontinue Nicholson Patternmaker's Rasps Because of Quality Issues
VintageSaws.com
