Most non-drop bars do not have a lot of bends in them, and they dont tend to be too tight. Also some people are just welding them, there are some threads of interest on the Frameforum, and there may be one more here.
You dont have to pack the inside of a tube in order to bend it, it becomes and issue with the thinest wall sizes. Its a ratio thing, with wall thickness in proportion to tube diameter being the issue. The material you need to use is 4130 aircraft steel. That material is right at the crossover point where the wall thickness is really to thin, and it does need to be mandrel bent. Most builder are to scared to go that thin with the welding and unknown loads so they go to the next size up, and at that point the mandrel isnt required.
Cost wise 4130 is no problem, but you always need to make a few trial pieces to check out the dimensions of where the bend starts relative to your layout, and how much springback you get, etc... You are bound to ruin a few pieces, and the end result is you are going to spend more on this project than you think, so you need to have a reason like learning, customizing, making what you cant buy, or in my case the Thorn version being 200 bucks.