I had these made at Signorama not sure if this was what you were looking for. I had them made with hash marks on the side and bottom and just cut them out with x-acto knife. Was thinking about having more made. Also Rowan engineering have some also.
This is the style I’m referring too but I wanted someone else who is more knowledgeable make it for a professional look and accuracy. I really don’t have the time or the patience these days.