I own a Humane Restraint Straitjacket. The sleeves on this thing are very long. They used to use this in asylums, but they are considered outdated now. They do still sell these. You usually see this kind of jacket for performances.

This is the jacket you have seen my characters wearing, but this one doesn't have side loops to prevent the wearer from lifting their shoulders over their head. I'd like to get some sewn on at some point, but I have little to no knowledge of sewing machines and canvas.

Go ahead and use this for drawing references. All I ask is you credit me.