I used to go to a fabric shop and buy whatever cotton flannel fabric they had cheap.
Wash it to remove the sizing and cut into patches.
You can also use it to make your own silicone wiping cloths by cutting the fabric into cloth size pieces and spraying it soaking wet with automotive store spray silicone.
Once the cloth starts to get dirty, throw it away and make a new one.
This prevents wiping guns and instruments with a dirty, gritty cloth.
The guys on "The Box O' Truth" recommend using...... tampons.