USJ pass/express ticket advance purchase

Hi,
I've just purchased the admission ticket in the USJ website. Unfortunately it seems that the Express passes for the date (4th May) are already sold out! Don't know what to do now :(
Does that mean all the Express passes for that day are sold out including those inside the park or are these only the passes available online?
Also does anyone know if there are other places where I can buy Express passes in advance? (aside from USJ website).

We just bought our express passes and tickets at Lawson. Do we need to change these for booklets once we get to the park or can we just use the tickets printed by Lawson? These have QR codes on them, so I am assuming they can just scan the codes, just not sure. Cheers.

Hi
Your step by step is clear, however when I reach step 7, I start to be confuse, they prompt if we want normal or back drop hollywood, then there is a timing, i chose backdrop and it prompted me to select a timing but when I go in, I could only see the timing but no way to select it. Please advise.
Btw, do we need to sign up in order to purchase online tickets?

Thanks