I've been using Mini Gaggia lever for some time and now need to replace the group gasket. I thought that would be easy-peasy and bought standard Gaggia Classic gasket - but it turned out it's too thick and definitely won't fit. Does anyone knows what's the correct one and where can I get it? I know that Orphan Espresso sells a Mini Gaggia kit with piston & group gasket & shower screen, but I need the group gasket only.

PS. According to my measurements the dimensions of old one (a little bit deformed) are 71.5x57x9 [mm].

Did you try to contact Francesco Ceccarelli? If he doesn't have one, he might be a good source to find one.

Orphan Espresso sold me a replacement gasket and shower head for the Mini Gaggia, great service and not overly expensive. Plus being US, you'll save on freight.
They also have a copy of parts manual and original brochure for the wee chappy online. Happy New Year

Thanks for answers. Finally I managed to find a proper solution: #02280020 (originally for Nuova Simonelli models, 7mm thick) + 2x rubber shim #1190003 (each 1mm thick). Portafilter fits perfectly at 6 o'clock.