FWIW
Seeing that plastic bushing stirred a long forgotten memory. My RD 350 had plastic, shouldered bushings just like the one in the picture. When I removed them, They were badly worn and cracked. That bike had barely 6000 miles on it. I bought new ones but hadn't installed them. One day, at a good old fashioned hardware store, I saw bronse bushings of different sizes. One looked like the shouldered plastic swing arm bushings I had at home. I think it was for a furnace blower. I went home, got the Yamaha bushing and went back to the hardware store to eyeball the two and see if the bronze bushing would work. Well, it was too long, the inner diameter was too small and the outer diameter was too big-- but, it was close! I hack sawed the bushing to the proper length then, using emery cloth on a flat surface, squared it off. Then flipped it over and sanded down the shoulder side til the shoulder was the same thickness as the plastic one. Then, I drove a piece of wood into the bushing, drilled a hole through it, and using a long #8 or so screw, washers and nut, tightened the extending screw into my drill and using emory cloth strips, began thinning down the outer diameter to match the plastic bushing. Then, taking a large diameter drill and taping emory cloth to it, then winding it around til it would barely fit into the bushing, I opened it up til the inner diameter matched the OE bushing.
It was a lot of trial and error fitting but I got it so that once installed and the swing arm pivot bolt properly tightened, the swing arm (with nothing attached), would ever so slowly fall (pivot downward) by it's own weight. Total cost at the time? About $4.00 and hours of my time.
Older and (slightly wiser), I see my CB450K2 swingarm is so loose I can easily move my rear tire 1/2 inch side to side. I intend to buy one plastic bushing then hand it over to an engineer friend who has a machinist friend who can make me two bronze bushings-- probably for free.
If I didn't have a friend who had a friend, I would make that trip to the hardware store, find something close and then find some small machine shop to duplicate it in bronze. It can be done on a lathe and maybe a drill press. If they wanted more than $20.00, I'd do it (again) myself, at home, the same way I did it -- back when.