Plastic Regulator Washer...Source?

I’m trying to find the white, plastic washer that fits within the regulator’s connector, the one you tighten by hand to connect the regulator to the tank.  Thanks.

The ones I get from the gas supplier are solid, with no hole.  Does it matter?

It seems weird that there would not be a hole, I’ve never seen any like that.  The ones I get from my gas supplier are the fiber washers with holes.  How does the gas pass through if there is no hole?