My lucky day. Browsing through the Part Junkyard on the Builder’s Club website (astromech.net), I’ve come accross a member that offered a 300mm aluminium dome for sale. This one was from the 2011 run. After a few messages back and forth that deal was done and off it went on his side in the US. The fellow builder even threw in a Deutsch base plate (see photo). That was highly appreciated. Thanks again!