I get my chicken grit at a local feed store, but you can also get it at some Fleet Farm, Menards, Walmart, etc. locations. Here is a picture of exactly what I use. It comes in a 50 lb. bag.
Yes, pumice can be used too, although I've never used it. I've never tried any type of bagged potting mix specifically for succulents either.
Don't be discouraged if you don't see any changes in your plant while it's in the house. Your main goal is to keep it alive until you can get it outside. Then you'll see changes. I would give it a bit of water every week - with our furnaces running all the time plants dry out in a hurry.
