Plastic card for fetal heart monitoring strips

Hello -- hope you can help me. I am looking for a plastic card that is a recognition tool for EFM strips. We have one at work but no ID on it to see where it came from. I've also seen some small plastic ones that fit behind your indentifcation badge; again, no ID. You simply place it on the strip and those with impaired vision (read my old eyes) can see clearly if the strip has an acceleration, moderate variability, etc. I hope I've explained it enough so someone can help. Thanks much!