you can probably get the gzipped source to install if you set the POSTGRES_INCLUDE and POSTGRES_LIB environment variables before starting the installation. the newest postgresql installs these in /usr/local/pgsql/include and /usr/local/pgsql/lib. to simplify matters, just invoke csh, type
setenv POSTGRES_INCLUDE='/usr/local/pgsql/include' and
setenv POSTGRES_LIB='/usr/local/pgsql/lib'
then go through the build process (perl Makefile.PL etc.)

if it helps any, i've cussed at this a bit myself.