Flyers and posters you can print yourself
You can easily print these flyers on a home printer,
You can use them the size they are OR if you’re getting them printed professionally, you could mix and match them. It’s of course a better use of paper if you do double-sided.
There are also A3 coloured posters or corflute you could get printed at officeworks for about $20. You can use the A3 sizes to make larger ones as well.