Here you can find an integrated ams hub based on the original filament buffer and A1 AMS splitter.
To turn the Bambu Lab filament buffer into an AMS hub you only need this case and the AMS splitter for only $6/7€.
Many thanks to Urban 3D who made the design for the filament buffer replacement and inspired me with the idea in the first place.
You can order it directly at the bambu store:
BambuLab A1 AMS Lite Filament Hub
EU: https://eu.store.bambulab.com/products/ams-lite-filament-hub
US: https://us.store.bambulab.com/products/ams-lite-filament-hub
UK: https://uk.store.bambulab.com/products/ams-lite-filament-hub
If is documentation is required for the upgrade, please ask.
I recommend PETG or ABS for printing, not PLA.