Are both forms correct, please?

Hello Gianne,   

My try:

I would say only a is correct for two reasons: 

You need to use "for" to underline the period of time you wait.  

If you omit, you may mislead the reader. Are you waiting " a long time"? It will sound as if you waited a long time such as you wait for a person. 

Additionally, I suggest you use "for" ater wait. We say, "wait for me" ,as a simple example, not "wait me".

                                          
Hello Doll,

Thanks for your explanations! 

Best wishes,
Gianne