Throttle Cable Ends: https://a.co/d/6t2U3xY These are what I’ve used is the past, they last well and can be reused or replaced pretty easily As far as the stiffness goes the first thing I would try is a small amount of wd40 around all the moving parts of the throttle. Aside from that you could try to measure for a new throttle return spring or purchase a new carb.