Many vendors take Paypal. I'm not sure if Paypal has a policy against using them for firearm purchases, but I think I remember hearing they do. I don't know if that would extend to accessories as well. If you kept money in your Paypal account and you used it to pay directly to the vendor, would Paypal be coding those type of transactions? If they are prohibited by policy it seems like a similar service to Paypal could be set up that did not track purchases. Money transfer apps seem to pop up all the time these days.