Haneda airport

I have finally purchased my JR Pass! I've almost got all the kinks in my itinerary sorted out, but there's one last bit that is stumping me:

I will be arriving at Haneda Airport, in the International terminal, of course. I need to pick up our pocket wifi at the post office in the Domestic terminal. Is it possible to get from the International terminal to the Domestic terminal easily? I've read on Haneda Airport's website that the terminals access each other via the Tokyo Monorail for free with your passport and proof that you have a transfer between terminals.. I don't have a transfer I just want to get my wifi.