Mobility Aid...

[sandyRoe]

Is there such a thing as a Zimmer frame with wheels? I suppose it would also have some sort of brake to prevent it slippin away.

[ttfn]

sandy, a lot can depend upon how much shopping your sister would need to carry and the accessibility of shops. If these 2 matters are to be configured a suitable shopping trolley might suffice as they offer more capacity for holding shopping.

I know someone who uses a walking frame at home but for shopping trips uses a trolley. Some shops have steps at their entrance and a tri-wheeled trolley can be extremely useful to climb the steps with great ease.
http://www.completecareshop.co.uk/disability-elderly-aid/2293/tri-wheel_shopping_trolley.html

However, they do not have adjustable handles, so if your sister is tall that would be a problem. In that case a 4 or 6 wheeled trolley would be easier.
http://www.completecareshop.co.uk/categories-disability-aids/208/mobility_aids_shopping_trolleys.html

I realise that my reply does not take into account your sister's exact mobility limits, but hope it helps anyway :)

[sandyRoe]

She's a woman in her late 70s. Her hip pain started maybe a couple of years ago and has got progressively worse. She went for a scan a couple of months ago but is ignoring the doctor's follow up letter, won't make an appointment with them. She's burying her head in the sand.
She doesn't do any shopping now and the frame would be used to help her take her little dog out for a walk, a few hundred yards a couple of times a day.
Again, thank you all for the helpful input.