Contact cajon builders directly to find cajons made in Germany. Unfortunately most online stores and music stores only carry imported brands. Buying a locally made cajon cyles your income back through your local economy. Below are links to 11 cajon makers in Germany:

This page has links to the webpages of cajon makers based in Germany. Minimize the carbon footprint of your cajon purchase - buy direct from the cajon builder. Most imported cajons are shipped around the planet in big cargo ships. A locally made cajon helps your local economy and demonstrates that you are thinking about and support local artisans.

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.

One photo per German cajon manufacturer in Pinterest:

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.