These are our own creations from trial and error and all are wall mounted. We had so much fun designing them and couldn't stop at one due to the fact that each cat wanted to be on them. They all have their own with a design to match their personality. They are used all of the time even though they get to go outside and play. It is very important for your pet to be able to expend their energy especially if they are strictly indoors so this is a perfect way to accomplish that.
Here is a really nice portable cat wheel that has a 12 inch running base and is sturdy. I have one and can recommend this brand. Click US currency tab in the top left corner.