I also had to go with very shallow substrate for Charlie in his old age as he had difficulty walking. Another option could be to use hemp mat instead of substrate for the floor (it's intended for sick animals)and just have a pile of substrate in one corner for "playing with"
I get the hemp mats from Zooplus - they're quite cheap and very large - you just cut the size of piece you want from it and have spare to replace the existing piece if and when it gets a bit chavelled.
I think they still need some substrate at least in one area or under the nest, as their instinct is to bury things and dig at it a bit even when frail.
This Hugro one is the only one I've found any good. I did get another brand from Amazon once and it was awful and shed a lot and didn't seem safe. Rodipet do one that is ok as well.
https://www.zooplus.co.uk/shop/small...ll_pets/182988