It’s on amazon. Mix the powder with water and you get the paste. This is how (almost) everyone treats their tissue for origami.
Lineco Methyl Cellulose Adhesive 1 1/2 oz. bottle https://www.amazon.com/dp/B000KNLG1Y/ref=cm_sw_r_cp_api_glc_fabc_OiN9FbZTKRYWA