Even though one will last for many seasons, it's always wise to have a spare on hand. Now, Gunsmiths are very familiar with these and they do try and keep a good supply, on hand. Why not just go to one of your local Gunsmiths and see if they have one? Just make sure they are made of the proper elastomer and not neoprene. ...Anyone know a place that will drop
If you research this a bit, you will find a chart that not only includes physical properties but compatibility with certain chemicals. The chart really give you a great comparison. Neopene and or Buna-N is on the low end of the scale and Viton is much better. Does not mean that these low-end elastomers won't work; just means that they won't work as long as the better grades. Don't take my word for it, find out for yourself...Pahoo mentioned neoprene is a no-go. I don't know why