Alternative to chinup bar
Not that this helps you much, but it's an example of just looking around for things that can bear your weight to do excercises with-
I've been saving up to get myself a nice power rack w/a chinup bar attachment. In the meanwhile, I've been looking around my house for places to do chinups. Unfortunately the doors and walls aren't good for bearing loads as most of my doors are the sliding pocket type. It just so happens that I drained my pool for the winter so that I could resurface it - lo and behold, my new pullup equipment: the diving board.
Anyways, look around, who knows what could be used for pull ups (happen to have a balcony or open staircase?)