John Walton wrote:

the heat sinks in my Digikey, Mouser, etc. catalogs aren't of sufficient C/W
capacity (2 - 5 C/W). Can anyone suggest one or more sources which will
sell for TO-220 style devices in small quantities?

Are you willing to drill holes?
http://www.wakefield.com/pdf/Extruded_Heat_Sink.pdf
These are available from Digikey.

--
John Popelish