Design mechanical mechanism simulating breathing effect

In this project I'm looking for someone to design a mechanism that will be put inside an enclosed fabric and give the effect of breathing. We've had such a mechanism produced for another project a while ago. I do not currently have more pictues or videos of the mechnism itself doing its work. I might be able to supply later if it is needed. Note that the mechanism you design doesn't have to be designed exactly the same way, but for the right person the attached pictures might be telling of it's workings and serve as inspiration. This time we're trying to achieve the same effect, with a mechanism to be designed with the following goals: It runs on battery power, and should ideally be able to run for 8 hours minimum at a time, before charge or change of batteries. The idea is that you draw up a working design that can be fabricated locally using readily available parts. This could be arduino, nema 17's, or other common servo-motors or something else as long as it is not to exotic and parts are easy to order online. Another good thing would be if most of the "structural" and moving parts could be 3d-printed, so that we can print these as well locally. Although being able to 3d-print the parts is not a definite requirement. If it makes more sense for durability of the mechanism for some parts to be aluminum or steel we are absolutely open to that. You should also provide a simple animation of the mechanism and its way of movement for us to be able to see the idea before we decide to go ahead with actual production with it. This time the plan is to put the mechanism in a backpack similar to the one in the attached picture. We would like copies of all relevant final design files. We would be delighted if you use freecad, blender 3d or other open source software for this, but this is not at all a requirement. The most important goal here is that the final design is not too difficult to build locally and that its operation is stable over time. It should be able to run unattended for longer periods without mechanical failure. Also the motion is important, it should be as smooth and have the same "feel" as in the attached video. I am not even sure I will find the right person on freelancer, but please do bid for this if you have the relevant experience and skill set. Do also link to other relevant projects you accomplished in this context. Also there is no rush to submit your proposal, we will probably wait at least 48 hours to look through proposals and applicants.