Not all stainless steel is the same. There are so many different types of stainless, very high quality stainless has a high nickel content.... and you will know it because it will not stick to a magnet. That is why almost all pins that say stainless on the package are not high quality stainless and will rust under the right conditions.
I purchased some plastic coated paper clips to use. I also... if I have to .....pin fabrics at the selvage if they are going to be stash fabric. I have also used fabric trimmings to tie around a roll or board of fabric. I did try rubber bands at one point but over a long period of time they did leave a slight stain.