Go to The Taipei City Hall Station MRT, take exit 3 and walk up Zhongxaio road away from the downtown area. You will pass a firestation, then on your side of the road there are a lot of shops. There is a sex shop right in there, not too far down. Not sure about the actual quality, or seediness of the place, but see it when I'm out for walks. They have outfits and toys right in the window, so your... friend... should be able to find what they are looking for there.
"Nothing Worth Having Comes Without Some Kind of Fight. You've Got To Kick at the Darkness Till it Bleeds Daylight." - Bruce Cockburn
"A Man Is a Success if He Gets Up In The Morning and Goes to Bed at Night, and In Between Does What He Wants to Do." - Bob Dylan
"Goonie-goo-hoo" - Eddie Murphy