Dell'Orto MA19B6 - airfilter tipo F18/1

One of the things I had to look into was the carburettor as it has now a silly open air filter and not the original filter housing. 

By now I know it's a Dell Orto type MA19B6 and the correct matching filter should be a tipo F18/1 and not a F18 (without /1). The difference apparently is the opening, the first one is oval and the other one is round. Maybe not a huge difference but judging by the photo's the F18/1 has a much larger opening, so more air intake. 

dismanteld Dell Orto MA19B6

When checking online I found this photo with the correct setup (however a 2nd series).
In this case you can see clearly it's a tipo F18/1 filter with a tube connected to a seperate airfilter box.
So I now need to source those 3 items: airbox, airtube and carburetor airfilter housing. Where to find this?