it's tr2post, which needs a postscript version of the character.
there's a euro-site that gives the amazing rules for forming the symbol
(protractors at the ready, gentlemen!) which might also have ready-made
postscript for conversion to whatever tr2post might expect.
there might also be a newer version of /sys/lib/postscript/font/lsunr20.pfa
that includes it.