I think that’s 天水路 Tianshui Road, off a circular intersection near Chongqing Rd. and Nanjing W. Rd… Here is the online info from one of the stores there, which has both chemicals and DIY cosmetic ingredients, so you can call them for directions:
Address: No.43 Tianshui Road Taipei City
TEL：(02)2550-1101
Opening Hour：8:00~18:00 （Saturday until 17:00、Sunday and Holidays closed）
And here is a map:
Look for the red dot
http://gis.nat.gov.tw/village/search_road.jsp?s_county=tpec&s_road=121
You can buy dyes for clothing at stores in this area, DIY styrofoam or epoxies, acetone, etc. Note that they tend to keep short business hours, though.