Truck Sim

I wish I had space for a simchair rig but I have to use my normal chair for my driving sims. The only catch is the wheels on my chair are extremely sensitive so when I apply any pressure on my pedals I actually roll backwards haha.

I currently just use an old rolled up towel but was looking for a more permanent solution like something I can just slide behind my chair. I've checked the manufacturer of my chair (Herman Miller) don't sell lockable casters and don't recommend 3rd party parts =\

I'd almost say it's a job for a 3D printer but I don't have one either haha. Any suggestions would be great!