These are made for wood fences and are the most common option on the market. You’ll find loads of designs with different decorations on them, too.
Vinyl wall toppers for privacy come in all kinds of designs, and they’re all weatherproof. As the name suggests, you can fix them to brick and concrete walls with anchors.
While not technically a privacy topper, you could use a roll of fake ivy to increase the height of a wall or balcony railing. You’ll need to include supports, but you could use anything sturdy.
These don’t really count as privacy toppers, but they are a good option for renters. If you have a balcony with railings and you can’t do anything to them, consider standing a panel behind them instead.
Some composite fence panels would work as wall toppers for privacy. With the right installation, you could probably fix them to iron railings, too.