On a recent trip my passenger side front seat (84 Westy) coughed up a small bit of plastic.  Later, during a seat adjustment, it ejected a strip of black plastic about 6 or 8 inches long.  I recall seeing this piece when I had the seat removed in the past and supposed it was some sort of sliding shim that help the seat move yet remain stable.  Anyway, it's apparently toast.  The questions:

Are these available?
Would there have been 2 per seat originally?
If they are NLA is there a alternative?

Right now the seat seems to have a lot of side-to-side wobble and as the bolts on the 'turntable' are snugged up I expect these missing pieces are the cause.  Not bad on the long & straight roads but most of our driving is mountain twisties and my passenger doesn't care for the extra tossing about.

TIA for any advice offerred.

Geo Hahn