I run N-Gear catchers on my gravel and road bikes. They are cheap - around $12. When properly set up, it works great! Knock on wood, but I haven't dropped a chain in months, while it used to be a common occurrence.

Just be careful that you set it about 1 mm away from your chain when you are in the small front/big back gear combo. Any farther away, and you can drop the chain through the catcher, and it is really hard to get it back out.