I've used agar before in my Maple-Pecan Milk Foam at a 0.75% ratio, just blend it after it sets then add to the whipping siphon, charge, and dispense. You can also try using iota carrageenan in a 0.75% - 1.0% ratio.
Here's two recipes from my book
The Whipping Siphon. I think either would work ok with almond milk too, though you might need some more carrageenan because of the lack of dairy.
Agar Mango Foam
Pour 400 grams of fresh mango juice into a pot and add 2.0 grams agar (0.5%) to it. Blend well with an immersion blender. Bring to a boil and let simmer for 3 to 5 minutes. Remove from the heat, pour into a container, and let cool.
Once cool, use a standing or immersion blender to blend the mango agar gel until smooth. Add to a whipping siphon, seal, and charge. This foam can be used both on hot and cold dishes.
Carrageenan Chocolate Milk Foam
Combine 400 grams chocolate milk and 2.0 grams iota carrageenan in a pot and blend well. Heat the mixture above 70°C / 158°F or as high as a boil. Remove from the heat, pour into a container and let cool into a gel.
Once the gel has formed, blend it until smooth and pour into a whipping siphon. Charge the siphon and it is ready to dispense. The chocolate foam can be served either hot or cold.
