I sourced a place locally that carries rather large ziplock bags. I'll have to check to see if they have bags big enough for 14x17, but I'm sure that they do. Developing with a ziplock bag is easy. Just place the bag in a tray, slip the film in, pour in developer, seal the bag up with just the slightest opening, then puff in some air from your mouth to keep the top of the bag from settling on the film, seal the bag all the way, agitate as desired, and Bob's yer uncle. After development, just pick up bag by corners and pour out developer, pour in stop, dump, pour in fix. I use a hardening fixer.
If you cannot find large ziplock bags, a heavy duty black plastic garbage bag works well. I like the ziplock bags, as you can see through them. Kind of nice being able to develop xray film (green latitude type) under a safe light rather than the dark.
There is a good thread concerning xray film here: http://www.largeformatphotography.in...=48099&page=31