If it's short term she might find a charity that will loan them out.
Supermarkets loan wheel chairs for shopping but some are better than others - space in isles & manoeuvring around displays. My mum likes sainsburies best.
Also look into the local towns & see what they do for motorbility. Although she doesn't want to buy a motor one a lot of towns centres hire out motorised ones while you are there shopping.

Having a good hunting stick maybe another help too, then when she does get tired she can sit.

I've asked my mum for other suggestions & will post when I get them.