TMPGenc as already noted will do an excellent job. A decent enough
freeware joiner is CombiMovie. I've had glitches here & there joining,
bit it's OK if you need a quick joiner.
http://www.bobyte.com/
"CombiMovie should be used to combine only files with the same
characteristics (same dimension, compression method, color depth etc).
CombiMovie will not check whether these are true before joining, but
off course you may try to join two different characteristics of movie,
and see what happens. In many cases it will still be running. "