Where can I find suitable replacement tubes for AC/DC tube radios?

For AC/DC tube radios, the correct U-series tubes and a technically suitable selection are especially important. This applies, for example, to models such as Grundig Musikgerät 87, Grundig Musikgerät 95GW, Grundig Musikgerät 3028 AC/DC, Schaub-Lorenz Touring T50 Automatik or similar AC/DC receivers from that period. Typical tubes include UABC80, UY85, UCH81, UF89, UL84 and, depending on the unit, other U-types. Especially with AC/DC devices, it is important not to use just any substitute, but to choose the tube set that matches the specific device.