It is highly unlikely unless it has been run over, that the spirit burner from your Trangia cooker has stopped working. It doesn't have any moving parts, and it's made of brass, so it wouldn't have rusted.
The most likely reason you need a replacement is that... well, you lost it. Or maybe you have an engineering mind and have constructed your own compact camp stove from sheet metal and wire, and the Trangia Spirit Burner is the final touch.
Whatever your reason for needing one you can rest assured that the Trangia burner works, its simplistic design remains virtually unchanged since the mid-1900's and plays a key part in the longevity and reliability of any Trangia cooker.