Here's what the folded card looks like (the paper used in this one is available on Etsy). If you're delivering it directly, no envelope is needed, and as you can see in the front page of the video, there are lots of decorative papers that can be used.
Or how about a star card? This one's available on Etsy.
Or, you can make your own. This one has English subtitles, but I found that useful, because I like having written instructions.