sos-tatra.cz is an early supplier of general parts and can also do restorations.
tatra603.cz (Jan Papirnik) specializes in body parts and can also supply other items. A friend who ended up restoring the rusty burgundy T603 in the "Video" section has dealt with him and speaks highly of him.
Parts are available on the web from various specialists in the Czech Republic. Suppliers generally have an English version of their website (look for the British flag - click to switch to English). The following are links to some suppliers:
tatravintage.cz carry general Tatra parts and many English-speaking Tatra owners use them and recommend them.
bekas.cz specializes in brake parts for both vintage and newer cars. They have some special components that Tatra Vintage doesn't carry.
This section contains other miscellaneous information and will be updated as needed.
ecorra.com is known as the premier Tatra restorer in the Czech Republic. They specialize in pre-war high-end models.