Well . . . 3/8 inch is .375. I got mine from Haror Freight. I've used it to make wads from scrap leather from my holster making and leatherwork. I punch 'em out and then soak 'em in a hot batch of Crisco/toilet ring wax - simple to do - combine the two in a plastic container and microwave. I melt the two together and stir it - drop in the wads and then use a small cooking strainer to dip them out. Put them on a number of layers of paper towel - let 'e, cool and then store them in old Altoid Mint tins. For me, they seem to work fine. You can do the same with wool felt.
If a pair of '51 Navies were good enough for Billy Hickok, then a single Navy on my right hip is good enough for me . . . besides . . . I'm probably only half as good as he was anyways. Hiram's Rangers Badge #63