What specifically do you want? I have:

https://github.com/pjlsergeant/byre -- slightly different security model, but lazer-focused on developer experience; my daily driver and I love it not just because I wrote it. The TUI is great for configuring and setting up instant boxes just how you want

https://pleasedonotescape.com/ -- a list of every other agent jail I could find, filterable by open-source and whatever else you want