No, there are no official updated iso files between the released versions.
But there are daily built iso files of all versions being developed, the 'next one' now 23.04 to be released in April (a short-life version) and the currently newest LTS release, now 'jammy' alias 22.04.x LTS. Those iso files are published at the ISO testing tracker for testing purposes, and you are welcome to use them.
I would recommend 'jammy'. If you use it to install, you may want to turn off the 'proposed' repo in the installed system in order to avoid getting versions of programs, that are not yet tested and accepted.
As indicated by oldfred, It is a good idea to use an SSD connected via USB instead of a pendrive. It is faster and much more reliable, responsive enough and big enough for heavy updates & upgrades. So you can keep a persistent live system up to date with
sudo apt update && sudo apt full-upgrade
without problems (I have tested it with many repeated updates & upgrades).
But it is better, easier and more reliable to get a fresh iso file from the ISO testing tracker instead of keeping a persistent live system up to date. Also, if I remember correctly, persistent live upgrades will not affect the installation, so if you want to install up to date program packages, you should get a current daily iso file.
If you use zsync
you need to download only the modified parts of the iso file since your previous download and there is an automatic checksum test. Details to install and use zsync:
sudo apt update
sudo apt install zsync
zsync http://cdimage.ubuntu.com/jammy/daily-live/current/jammy-desktop-amd64.iso.zsync
I suggest that you run zsync
at home or some other place where you have a fast internet connection. Then you can use the up to date live system where there is a slow internet connection.
Finally, you are welcome to (but need not) participate in the ISO testing and report bugs ;-)