comments:
It would help to know what country. Here’s an option that Amazon America has that’s relatively cheap. You may have sometime similar on your country’s Amazon. https://a.co/d/0iEFH8Bj And if you don’t care for longevity there are always thumbtacks. It will destroy the poster and will make it no longer desirable for any subsequent sale. But you have already said that you don’t care about that. You could use the thumbtacks, not through the poster, but with the shank right next to the poster edges so that the heads of the thumbtacks are holding the poster in place instead of the shank going through the poster. The sticky putty will also work but will discolor the back (and eventually the front) of the poster. Also, wheres the photo of the poster. We wanna see it!