I'm not sure how portable this method might be but you may be able to adapt the concept to your specific needs.
I did some work with Growing Power out of Milwaukee teaching folk in food deserts how to build hoop houses out of readily available, inexpensive material. We used standard chainlink fence pipe as the support for the plastic sheeting(I believe it was 1 3/8"). We built a jig on a sheet of plywood with 2 7' lengthes of 1"x3", some trapezoidal shaped pieces of 2"x4" some wood glue, screws and 2 firring strips.
First we secured one 1"x3" perpendicular to the plywood with a couple of screws.
We screwed the second 1"x3" into the far end (not attached to the plywood) of the first piece so it would swivel the arc across the length of the plywood. Once the arc was drawn they can be removed.
Glue and screw the pieces of 2"x4" along the length of the arc.
Glue and screw the firing strips into the blocks thereby creating the arc.
Glue and screw a longer section of 2"x4" along the far end spaced so that the object to be bended just fits in the gap.
Insert the pipe in between the longer 2"x4" and the first trapazoid of 2"x4" and slowly pull the pipe down until it hits the arc, slowly move the pipe up and continually bend the pipe down towards the arc.
Voila, you're left with identical pieces of bent pipe.
The arc we worked with was more severe than what you're describing (essentially a half circle) but if you can get the bend you want down once this method will allow you to duplicate it.
We were working with 31' lengths of round pipe and it really helped to have a second set of hands to hold the pipe flat against the plywood .
Slow and steady will prevent the pipe from crimping (I don't know how this will work with square pipe)
Here's proof that I don't have an artistic bone in my body:
I hope this helps.