I upgraded my Messmer itabag ☺️ I bought a new bag with a similar insert window size, so if i want to swap inserts between bags it will be still possible.
The new bag is from a Chinese brand called AORDA, they have many designs of various sizes, and the quality is amazing. The bag is slightly bigger than my Puffken bag, close to a size S WEGO bag. It's so so spacious inside with a lot of pockets and side pockets. The pocket to place the insert is inside the bag with velcro for opening. I bought a few accessories made for WEGO bags - the red ribbon and the pearl chain to decorate and they fit perfectly. It includes a clear insert board along with a long strap with shoulder support so you can wear it as a cross-body bag.
My favourite part is inside there are 2 mesh pockets in the sides. You can put in there a water bottle, sanitizer, an umbrella, or lightstick for your concert needs without having to worry it flopping around in the bag.
The weird but good thing is that it does not feel heavy at all carrying that much stuff on my shoulder. I understand why this bag is x3 the price of my Puffken bag lololol. I got it during a mega sale just for 103 Yuan (around $17), original price was 209 yuan (around $33)