Amazon has some things that might help you
https://www.amazon.com/Vive-Crutch-Accessories-Bag-Orthopedic/dp/B0882GFJH5/ref=mp_s_a_1_7_sspa?keywords=cup+holder+for+crutches&qid=1649382441&sr=8-7-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUExTFM3T1A2TDdDS1JUJmVuY3J5cHRlZElkPUEwMDM4OTE0MzZOMkVXSlQ3UjJFViZlbmNyeXB0ZWRBZElkPUEwOTk3Nzc3UFpJSE9PSUI4TTgmd2lkZ2V0TmFtZT1zcF9waG9uZV9zZWFyY2hfbXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==#immersive-view_1649382484926