No problem. I found this on my hard drive from a question asked like yours in the past. You can buy these in any dental supply store that will allow 'cash' purchases for non accounts. It may need ordered if they don't actually stock anything though. A lot have gone to central facilites.
Left to right here is soft, medium stiff, standard stiff and extra stiff. They last a long time. I bought a box of each one in 1997 and still have about half a box of each one left out of a box of 12 each. I've used non dental ones but they are not as good. Having a dental background my wife and I have an account with Patterson Dental so we just order them and some other things like small carbide burrs and the like when we need them. The draw back is that anything labeled dental ain't cheap but they do work. Good luck.
STR