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Try an automotive replacements parts dealer, They will know what you are looking for. They should (used to)    be able to oblige-They are used for bearings in alternaters and etc and are usually self lubricated, normally sold separately.Mention "Sintered bronze bush" (bearing). sinterered is compressing the fine bronze dust under high pressure into a fine tollereance mould the bearing is sized and finished to size in the mould so no machining is required. Good luck, Pardon the English spelling!

The link you posted is for purchasing a single pivot bushing for $3.95 US which is great. But the company in is Canada and shipping to me in California is $15 plus tax putting the single bushing at just under $20. Better than $100 for 8 bushing. I will do some more checking and chat with the Administrative Pastor if they want to pony up $20 to fix the chair.

However, you don't have to buy from McMaster Carr. The addition of S/H $$$.Since you're in California, Orchard Supply Hardware carry nsk bearings of this type.They might have the one you need.If you choose to pursue this route, the next thing is to put a hex head cap screw.through the bearing and fasten it together with a nut on the other side.I think the relief pocket (3/4x1/2) is big enough to accomodate the head of the cap screw plus deepening the bore for the bearing.

The next step of these free plans is to cut and install the rocker arms and bearings. No matter what type of stock you used for the base and the chair, the rocker arms should be cut from hardwood, since the entire weight of the chair and the occupants will be on these four pieces of stock. With your circular saw or compound miter saw, cut four 1x4 sections of hardwood to 14" in length. Round over the corners with a 1" radius using the band saw. Then, make a pencil mark 1-1/2" in from each end on center (1-3/4" from the edge) of each board. These marks will be the locations for the iko bearings and bolts. 

On the outside edges of the chair base, make four pencil marks for bearings as well. Each mark should be 1-3/4" in from the ends of the rounded top board on each end of the base, and 1-3/4" down from the top. Finally, on the insides of the curved base boards on the bottom of the chair assembly, we'll need four marks for the glider rocker bearings as well. These should be 1-1/2" up from the bottom. Measure 8-1/2" back from the front end of the curved chair base board, and 6" forward from the back end of the chair base for the marks.