Something thin to put between two pieces of 1/8" thick 1 1/2" wide
aluminum flat bar that are bolted together. A bearing that will
allow the two pieces of aluminum flat bar to be held firmly together
but move (the only way possible) against the spacer between them
with as little friction as possible.

Would that be nylon? Delrin? What is it called? At the moment, my
best guess is "thrust bearing". Even though the only thrust pushing
the pieces together is the bolt that holds them together. I'm
looking at McMaster.

Is there something not officially labeled as such that works well
for that purpose? I have some spray Teflon silicone lubricant from
Lowe's.

Thanks.