That depends on what you call a decent price... In your location (Romania), finding a local metal supplier who will sell you small pieces will be the challenge. To mail order the material, international shipping comes into play. For the few meters of tubing you seek, shipping could cost more than the material. I live in the USA, so mail ordering the tubing would be much less expensive.
It may be worthwhile for you to make your own. If you can find inexpensive soft copper tubing, the process is not super difficult. You have to make a tool to do it, though. I'm always short on money, so if I was in your location, I could definitely justify the time and labor to do it myself. Knowing someone with a lathe would save lots of time, but with this type of tubing, you could do it by hand.
Here is a super industrial version of the method:
Straight off the top of my head, I would probably make something resembling a pipe threader head with wheels instead of thread dies in it:
