Does anybody know where can I fix a Sony walkman from 20 years ago in Tokyo?

I found a good Sony Walkman sports In a Hard off but I noticed the cassette isn't spinning so probably the problem is located in the drive belt and needs to be changed for a new one. I will still be in Japan for one month and a half so I thought about taking it to Akihabara but I do not know where. If someone knows some vintage shop where they fix old walkmans I'll be really thankful.