I wasn't able to afford the fragment pack for walking tomb dreng the first time it appeared.  I can now and I really want him.  I have 70 fragments.  Will the fragment pack be available a 2nd time?

I have never heard of one being available a second time.

Although no promises they will continue, but Plarium does do Fragment Top Up events once a year. So during the following year you can go back and earn some number of frags towards specific old champs. These have happened in the Fall typically, around Halloween last year.

So will I be able to get walking tomb dreng around this halloween?

IIRC during those aforementioned top up events they offer fragments for the second time if you fall short. 

I am not being rude but this game is never fair to your advantage.  This is a business.  They allow f2p to play.  I have 10-15 champs with partial frags.  Wait patiently and something special might happen to help you.  The one thing I have learned about this game, the unexpected can happen.  

Good luck with the game.  

If I have to wear my Wile E Coyote costume to win frags there better be a lot of them.   :)

Where did I put the dynamite?  And anvil?