I didn't find any alternatives, but I did find this information that might help with researching other mixes that might be similar.
What’s in Plantapon® SF?
10% to 20% sodium cocoamphoacetate
5% to 15% glycerin
5% to 15% lauryl glucoside
5% or less sodium cocoyl glutamate
5% or less sodium lauryl glucose carboxylate
the rest is water to a total of 100%
and sodium chloride (salt) at 4.5% to 5.8%.
As a note, it can be called all kinds of different names, so look for this INCI: Sodium cocoamphoacetate, glycerin, lauryl glucoside, sodium cocoyl glutamate, sodium lauryl glucosecarboxylate. It may include water somewhere in the list.