I use this 3 ring binder: https://smile.amazon.com/dp/B079NN9ND1/ref=cm_sw_r_cp_apa_fabc_26FHAQBBZFNJ57735TR9?_encoding=UTF8&psc=1

I use the euro mini card sleeves on my items and have them all stored in these pages without a problem: https://smile.amazon.com/dp/B01CTY7LT2/ref=cm_sw_r_cp_apa_fabc_YN0CPWTDWH2HK11RXWP8?_encoding=UTF8&psc=1

I like to use that type of 3 ring binder because I use the expanding files for character sheets, rule books, scenario books, sticker sheets etc.