Well, boots of the fox are slightly SLOWER than boots of speed i think.
Anyway, you can find them in the Yuan Ti mountain, in first floor. There is a Statue near the Yuan Ti leader, they are there. Maybe you havent found them the second time causein IWD items are RANDOM, that is, there are normally 3 or 4 choices and any of them may appear in the same place. For example, in this statue, you can find the boots of the fox OR a potion of constitution (that raises your constitution 1 point permanently) or another thing that i cant remember.
------------------
"Let my spells do the dirty work" Ertai, High Sorceror of the Holy Flame