I had the same problem trying to find a set. Naive me thought Apple Store would loan me the tool for a brief time. NOT a chance!
In Canada, Home Depot, Rona, Canadian Tire don't have it. A friend helped me and I lucked out to find the Calgary physical store to buy this
http://www.princessauto.com/pal/product/8458432/Precision/32-pc-Precision-Screwdriver-Set which is exactly what I need.
If you don't have a princessauto or can wait, you can order the screwdriver set online from them or other places. Good luck.