Google Maps
📍 湘林特產行 gift shop
Souvenir shop by the parking where, among huge number of souvenirs, they sell interesting pin showing regions of Taiwan (see photo: https://maps.app.goo.gl/2B8a6eThAPCmf5QN7) as well as a set of 5 interesting pins called "Five wonders of Alishan" with famous scenes and places in the park (see photo: https://maps.app.goo.gl/i1ZZQjyxC9Q7hmsC6)
Google Maps
📍 阿里山特產行 gift shop
By the corner of the building with a lot of gift shops by the parking lot - there is a store which has nice pins about Alishan and Taiwan bear. I'm not completely sure the GMaps link shows this exact shop as I didn't save the name, but location is correct. See photo: https://maps.app.goo.gl/1JvgxMTNqPDDMzNp8.
Google Maps
📍 Alishan Visitor Center
They have a small gift shop with original souvenirs, and they sell quite unusual pins, which seem to be about Alishan... animals and trees? But look more like a modern art, but look quite interesting! See photo: https://maps.app.goo.gl/tbNZzZcQwDSQtWoV9.