Texas Tactical Supply has the Infinity Ultra fo $15.99 and the new Infinity Sonic for $12.99. Texas Tactical Supply is also very reasonably on shipping.
The Sonic is supposed to be just as bright as the Ultra but smaller using one AAA battery instead of a AA. THe Ultra is a fantastic light. I have carried one continuously for over 10 months and deployed overseas with it. I now carry the Sonic on a lanyard at work but the Ultra is in my pocket the rest of the time.
Link:
Texas Tactical Supply

Hope this helps,

Turk