There are plenty of choices for the 19/16 combo because that's what the super mini MX bikes are now.
Michelin MS2 starcross mini is an excellent choice (and my #1 choice)
Dunlop 756, 739, 773
Bridgestone m201/202, m77/78
Maxxis Maxcross-IT
and others -- good place to find them pretty cheap:
http://www.americanmototire.com/