I'm not totally sure, but I believe you can still get the Clicker system from K2. Could be a good solution. Maybe one BA or Nivek know something about this?
You gotta figure out how to remedy your arthritis man!
Pretty sure you're closer to that landfill full of Clickers up in the NW than we are.
There is the Kwicker system but that's for splitboards and as I haven't tested it yet I'm not sure how practical it actually is. Nor do I think even with some DIYing could you get it to work on a solid board.
So you have arthritis. It's not the end of the world for you, I have it. In fact it's flaring right now in my hips as I type this due to the fact I'm positive it's snowing up the street from me. The best way to mitigate it is to exercise, stretch, and look into supplements/enzymes that can help you. Or just don't snowboard. Harsh reality but the truth.
Solucien is right there is an EST compatible disk for the Flows and that could be an option. I would rule out attempting to bother with the K2 Cinch tech as it's a pile of shit. The APO Dual Tech though could be an option as well.
But honestly don't sit down to strap in do some yoga, do some exercise, and learn how to bend at the knees, hips, waist, and back to strap in. It's not that hard. If my geriatric ass can still do it a couple hundred times a day I'm sure you can too.