The following soy milks do not contain any chometz ingredients:

Soy Dream Original enriched soy milk:

Anyone for whom it is necessary to consume kitniyos may drink these products. However, because we are unable to verify the kosher for Passover status of the equipment on which they are produced, we recommend purchasing these items before Passover, at which point any traces of chometz would be batul (nullified).

Another alternative would be to use a Kosher certified almond milk which does not contain chametz .
The following are OU certified Almond Milk in the “original” variety that can be used for infirm and children who need an alternative to standard milk on Passover:

365
Almond Breeze Original (the refrigerated version does not even contain kitniyot)
AlmondSense
FredMeyer
Friendly Farms
King Soopers
Kroger
Laura Lynn
Market Basket
Nature’s Place
Ralphs
Roundy’s
Trader Joe’s
Tree Of Life