- Try contacting the wheelchair companies - they may have some suggestions, ideas, or even solutions. Likely that you have done so; however, even if so, keep trying. You may just need to find the right person to listen and act.
- Reconsider the problem. If the requirement is for less force then a micro-joystick may not necessarily achieve that. What may be needed is more leverage. Which implies a longer arm on the joystick. Or perhaps "weaker" springs/contacts in the joystick.
- Are there any universities or colleges nearby? Especially one that offers engineering courses? Many such schools are continually looking for undergraduate and graduate students level projects. The students do the research and physical work under the supervision of one or more faculty members. Some projects are long term and the assigned team can change and evolve with the project.
- Likewise look for local engineering companies that may be willing to provide help. Many companies sponsor or get directly involved with various projects. For Public Relations of course but some companies do want to help and their engineers can benefit in many ways from what they learn and do.
- I did some googling using "Wheelchair joysticks". Found quite a number of links and some links were for universal joysticks in the sense that they would work with a variety of wheelchair makes and models.
For example (not a recommendation or endorsement):
Do an initial search and then revise the search criteria as warranted. Many generic or universal designated products often list the devices that they are compatible with or otherwise support. Sometimes not fully accurate for one reason or another. Such problems might be resolveable by simply switching a couple of connections.
Contact a few of the wheelchair joystick companies if any of their products seem viable for you.
Lastly: switch sensitivities are measured in dynes. Gamers/ mechnical keyboards use grams. That is the amount of force needed to activate or actuate a switch.
Delving deeper: Mechanical actuation force.
Take a look at the current joystick(s) specs. There may be some specific number or value for the necessary actuation force. Knowing how much "less force" is necessary would be a useful value to have.
Likewise after googling a bit I found quite a number of links regarding actuation forces with respect to keyboards, joysticks, and robotics.
Again just do some googling and revising: you may discover other ideas and options to think about.
And someone else within this Forum may offer other ideas and suggestions. I have no problem with that.