Large Changing Bag 70 x 70 cm approx 27.5 x 27.5 inches
Simple changing bag, to load film into processing tank or load Darkslides. Double zipped.
If using one of these I'd get an old cardboard box that fits inside. If you remove one side & top of the box you can use this to make it easier to work in the bag.
I would suggest that once your up and running this would be one of the first things to upgrade. I would look at Harrison tents or the calumet one. Both quite a leap in price but will last forever.