Using a replacement AC-AC adapter that has a lower current specification
I guess you have no choice but to use what you can get, as long as you watch out for over heating of the transformer. If it is HOT to the touch, it is over loaded.

Another option is to buy 2 of them and wire the 16 VAC wires in parallel. Be sure they are in phase so you get 16 VAC at about 1200 mA of current. That should be plenty enough to run all outputs at full power. Also make sure they plug into the same AC outlet so they are in phase.