Urethane flexible socket rails are my portable toolbox/toolbag go to. They don't cost much at all, are indestructible AFAICT, and they hold sockets really well. Kinda weird to get used to at first, especially when new as they hold sockets really tight. You have to learn how to twist sockets as you push or pull them on and off and then it becomes super easy to do. You just give them a 90deg twisting motion and come off and go on easy peasy. If you try to just pull or push without the twist well, you're going to hate them because they are going to fight you.
There's nothing better or even close IMHO for a travel toolbox as you can grab a whole strip and take it with you and swing it around and toss it under a vehicle then drag it around with you then toss it back in your box, bag or bucket are whatever you're storing them in. and they don't let go of sockets until you want them to and you can't hurt them. If you drive over them with a truck you might hurt your sockets but you sure won't hurt these holders.
I bought my first sets (orange) in the 90s at Northern and I'm still using them. When I wanted more I found that Northern doesn't carry them any more so I had to keep looking and the only other place I was more recently able to find them was online though this welding supply company. WeldTab. where I bought several strips of theirs in red & black. Same thing just different colors.