Without knowing your environment, it's hard to say how I'd improvise pulls. You can set your feet up on a chair and do inverted rows against a table. A chinup bar is a great investment for this, as the chinup is one of the best upper body exercises available.
Actually, I have a pair of ten pound weights in my room I use during my evening routines. I know there is a name for this type of weight lift, but what about letting the weight hang and lifting it towards my chest? Making the pulling effort come from lifting it against gravity rather than lifting myself. Sure, it won't be much of a work out, but I can at least keep the muscles engaged and work them.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.