Have a look at the gerber river runner or gerber river shorty (shorty is blunt tip, all serrated blade). I have the river runner and it is quite adequate. There are a number of attachment options with the sheath, which is a big plus in my book.

About $25 for either knife through Amazon or Ebay.

I have no idea what the stainless steel is, but it's fine. And if you lose the knife, you won't be out a lot of money.

Another interesting option is the Cold Steel super edge or real edge knife(s). The blade is only 2 inches long and it's a three finger handle, but a good backup knife. Very sharp serrations.

Not useful against a hammerhead shark though.