Belly bands and vellum jackets for invites

What you are describing is the traditional full invitation set which is a rare thing these days. The invite is almost always larger than the inserts. Usually they are stacked. Invite on the bottom, details/direction card in the middle and reply card and envelope on top and that slides into the inner envelope. I’ve never seen a belly band or vellum jacket. In our circles, some brides use the old fashioned vellum sheet that sits on top of the invite that was used to blot ink and keep it from bleeding onto the other inserts, but many skip that and don’t replace it with anything. Get a sample sheet of vellum from envelopes.com and try it out to see if you like it. Otherwise save your money.

View Quoted Comment Thanks Michelle! I’ll try that. I wish that my invitations came with an inner envelope, but they did not. they just have the outer envelope and I was just trying to find a way to make them look a little nicer. Thanks for that website.

I went with the traditional belly band with my invite. It was not too costly, but really it's gorgeous paper meant to be broken (Minted sample below).
Depending on your wedding style, you can also tie ribbon. Some add a wax or faux seal to bind. I also found this video with a variety of diy options: https://youtu.be/LtKR3EQ960M

View Quoted Comment That looks so nice! I just hope since my cards are smaller it would hold together. lovely! I will check out the video too!!