This is casein glue like the white glue we all use in school ( kind of)

1. Add vinegar to lukewarm skimmed milk so it curdles.
2. Drain the liquid component off from the solids.
3. Put solids onto a strainer to drain off excess liquid
4. In a bowl, add a base (such as sodium bicarbonate, ammonia or washing soda) to the curds, bit by bit, until they change into a creamy mixture. You now have casein glue.
Note that what you have at step 2 is low fat cottage cheese, so this can be used instead, skipping step 1.

This preparation lacks the antimicrobial present in commercial glue, so will spoil in storage. It may be frozen in ice cube trays for later use, or made when wanted.

This is how things were done in the old days.  I don’t know if it works or not but if i had no other options i would try it.