[Crazy Canuck]

I haven't tried any of the commercial ones, but member Covert5 has a portable catchbox he made from a backpack that looks like it works really well. Extremely portable. Here's a post he shows a video of it in action. Best part is you might already own everything you need to make one

https://slingshotforum.com/topic/114820-2-bottle-caps-2-shots-wslingchucks/?p=1284036