Foobar 2000, a very versatile free program that a lot of us use for one thing or another, will do it easily.
Load the files to be joined into Foobar (you can even join a bunch of them at once).
Highlight the files to be joined.
Right click and select "Convert" then "Convert to Single file".
I use this for my line in recordings made with my Hi-MD recorder (you can't turn off automatic new track creation when the volume drops below a certain point and then comes back up). Once I had over 100 tracks in a set, and after converting to wave with Sonic Stage, Foobar easily turned then into 1 file in one step.