Xen: if you lost an item and can't find it, you lost that item... period. You cannot pretend to have found it, because then it's still cheating. If it wasn't cheating you could also "pretend" your characters were walking faster. No big deal that way.
Shadowkeeper is good for solving problems, bugs and stuff like that (when you don't get an item which you should've gotten anyway).
To answer your question, mabax the killer dwarf (love your name, btw, sounds like a bad teenage slasher movie
): there are enough Boots of Speed in the game to give your entire party better movement speed.