Where can I find suitable replacement tubes for portable, kitchen and battery radios with tubes?

For portable radios, kitchen radios and battery radios with tubes, suitable and tested replacement tubes in good quality are especially important. This applies, for example, to classics such as Philips Philetta, Philips L3D23T, Philips BX220B, Braun Koffersuper 100B, Telefunken Portable Hi-Fi and similar portable devices from that period. Types such as DAF91, DF91, DAF96 and DL96 are particularly sought after, depending on the device also DK91, DK92, DF96, DL94 or DM71.