I'm not sure exactly what these are properly called, but some syncro
Vanagons (I think only syncros) came with hard rubber flares that bolted on
to the rear ten inches or so of all four fenders. Replacements have long
been unobtainable but there is now a reproduction part available on ebay.

http://www.ebay.com/itm/VW-T3-SYNCRO-Bus-Radlauf-Schutz-Abdeckungen-mud-flap-schmutzfanger-4-pcs-/302296661635?hash=item466248fe83:g:VyAAAOSwpDdVMrt0&vxp=mtr

I purchased a set since they weren't too expensive ($80 for a set of four).
They are made of heavy duty fiberglass, not hard rubber, and do not have
the mounting bolts but otherwise they are faithful reproductions. I haven't
yet decided how I will mount them.

-Mark
Seattle WA
87 Syncro Westfalia