Recently, I managed to break my TRS-80 tape recorder. And, I was wondering if its ontopic.
No doubt, such questions are perfect on-topic.
While the recorder is for sure covered, you may still want to look for other, audio/electronics related sites, as there might be a more in depth knowledge about the specific device.
Can I ask about repair recommendations for Retrocomputing accessories?
Questions about background information (schmatics, etc.), how to do specific tasks and what material is needed are core business of RC.SE. Asking about where to get material is getting tricky, as explicit buy recommendations are not welcome.
Can I ask where I can pay someone to fix it (most convenient)
No, as that would be a direct product/business recommendation.
What's possible is to ask where to search/look for such specialists.