This page has links to the webpages of twelve cajon makers based in Germany.
YouTube playlist of cajons made in Germany:
Note that not all manufacturers have current YouTube videos. The list on this page includes websites and Facebook pages which may contain videos not on YouTube. The list on this page is current and actively maintained, the YouTube playlist is infrequently updated.
Listed above are links to the cajon drum builders in Germany as retrieved by Internet searches in 2018 and 2019. I am sure there are many others not listed. Please send me updates and correction if you have additional information. Thanks.