Where are they Located?
If you ride a Taiwanese motor bike in your country, it is cheaper to buy the bike parts in Taiwan.
There are bike parts that are not sold in your country.
The biggest motorbike parts shop is called 迪世亞重車精品館.
They are located near the MRT mingquan east road station.(Red line)
They are close to the station.
They are bike parts and equipment shop.
Address
迪世亞重車精品館
http://www.dcr-motor.com.tw/html/front/bin/home.phtml
Map
If you look for KOSO Motorbike parts shop, 優購愛馬機車行 is a good place to buy. They do back order.
優購愛馬機車行
Address:No. 667, Section 4, Bade Rd, Songshan District, Taipei City, 105
Map
You can buy online but their item online is very less.