There were two Octalink patterns, V1 which was used on most road cranks and V2 for most MTB cranks. Your 105 requies the V1 version.

You could use any V1 model, 105, Ultegra or Dura Ace, but the 105 is the only one in current production. There are two lengths, 109.5 mm for double cranks and 118.5 mm for triples and Licktons in Chicago has both of them for about $50. Look here and scroll down to find the one you need: http://www.lickbike.com/searchsite.p...ottom+brackets