How do I access Showtime on Demand on direct TV?

I have all of the Showtime channels but there is no on demand channel (channel 1545). When we spoke to the DTV rep they stated that we need internet access to access direct tv cinema which would include showtime shows. When I look through the Direct TV cinema channel, it doesn't look like what we are asking for. The problem is that I would need to get a wireless adapter to connect the DTV box to the internet since the box is on the other side of the apt. and I don't want to fork out $80 if it wouldn't get us the on Demand we were wanting. Us watching the last season of Dexter depends on a solution!!!!! Thanks for the help!