If the goods arrive in EU, you have to pay tax only one time. Inside EU there is no more tax - so if you ship it from Germany to Latvia, there is no more tax.
A frame costing less then 22 would be very unlikely to pass customs without taxation, but there are better chances to not pay tax when you ship it directly to Latvia. Our ex soviet customs don't have that "german accuracy" in their work - ask how i know
If you can get the HK person to help you, what you could try is: The seller should declare the goods as used and less then 22 euros and it would be a good thing if he could verify it (by email) to the customs when necessary - i.e. "it is a used frame discovered when i was cleaning up a garage, i didnt need it, thus sold it".
The downside is that the declared value is also the insurance value, so when the frame is damaged during the shipping, you get also less than 22 euros.
Greetings from Igaunija