I have a set of Instamold
earplugs that I use sometimes. I had them done at a gun show last year. Took about a half an hour or so total to have them made. They work really well. I don't always use them as I prefer my electronic muffs, but I have successfully used them, doubled up with my e-muffs without much issue. I believe they have a do it yourself kit also. But I'd recommend having someone do them for you if you can.