Does the cruise ship you are on have one? Seems like they would have some medical supplies. Wheelchairs, etc... Also seems like Juneau would have a pharmacy or medical equipment shop with walkers/canes/wheelchairs etc.
This is the first thing to come up in quick search:
https://www.ronsapothecary.com/durable-medical-equipment-dme This place might need an MD prescription, but maybe not.