I'm feel relieved.
what rare a souvenir in Taiwan?
I don't is it suitable for you...
duck tongue(鴨舌) and the egg which is black colour called鐵蛋 are famous souvenir in taiwan.
Also some sweets which is very funny! if you want to see i can show you:
i am not good at english, sorry that i can't teach you, but i can chat with you( ^ω^) 英語があまり上手じゃないので、教えてあげないけど、チャットしてもいいよ(`・ω・´) 日本語が初心者なので、間違えたらすみません(´;ω;`)