Here are some photos of a tube from a later Urania/E61/President.
Overall length is 230mm.
Brass end caps are 25mm, total length of end cap and electrode is 75mm. It means the actual glowing section of the tube is only around 80-70mm.
And here is the original against the 50 or so tubes I had made. The ones I had made do not have the custom brass end caps which plug into the tube clips on the Faema frame.
For the power to the tube you will need a transformer that will convert your voltage to high voltage >1kv to say 10kv. The output high voltage should be configured to the tube length and diameter. For the small tubes I have found the smallest 1kv transformer works fine. There is a formula I think but I just did trial and error.
These days no need to use a large clunky iron transformer but you can use a small solid state transformer, for example: https://www.partsforsigns.com/solid-state-neon-transformers/
There is no doubt that the glow from the neon is just incredible but you need to consider the safety aspects and insulate the thing correctly. Also you should use special neon high voltage wire from the transformer to the tube. The transformers will come with the high voltage wire but bear in mind if you need to extend the wire you need to buy the special wire, you can't just extend it with household mains wire.