Can anyone steer me to a website where the following or similar
expression by Panagiotis Kanellopoulos: "Makronisos is modern Greece's
Parthenon" is quoted?

I'm afraid I found nothing about Makronisos by Kanellopoulos. 
Would either of these help?

 ~ A book called "Makronisos the New Parthenon", by T Kontou:
http://www.mathisis.com/title/title.htx?UOYKD025470

 ~ An article in JOURNAL OF MODERN GREEK STUDIES, XX  2 (Autumn
2002?):
Yannis Hamilakis, " 'The Other Parthenon': Antiquity and National
Memory at Makronisos"
https://maillists.uci.edu/mailman/public/mgsa-l/2002-November/000940.html

Hope you can track down your quote - Leli

To leli-ga:
Many thanks for your efforts.
I don't know if you are interested in the subject of the "Latter Day
Dachau",
as 'Makronisos' has been dubbed, but here are some quotes from Gen.
James Van Fleet and Panagiotis Kanellopoulos on the occasion of their
day-long visit to that Hell, where pulled nails were welcomed by the
leftists detainees, in lieu of the more horrific alternatives.

Van Fleet's Feb. 23, 1949 statement(translated):
"For me, today's visit to Makronisos was one of the happiest days of
my life. Verily(truly), a national Baptismal(beginning). All my best
prayers(hopes, wishes, blessings) are directed to the brave warriers
of Makronisos."
Signed: James A. Van Fleet - U.S. Army.
To his defense, since he did not know one word of Greek, he only
signed what they wrote out for him.

Kanellopoulos's March 23, 1949 statement(translated):
"I am proud to have come face-to-face with(meet, behold) you, the men
of Battalion B, of Pioneers(vanguards, scouts, special forces). I
congratulate you and I promise you that I will remain
whole-heartedly(spiritually) next to you."
Signed: Panagiotis Kanellopoulos(Minister of the Armed Forces, not
included).
See PhotoClip, near bottom of    http://anatolikos.com/dse/dse86.htm

Cannot explain the disparity in the dates. I am sure that
Kanellopoulos, member of the Hellenic Academy, prolific author of
European Culture, was still in complete control of his immense
faculties.

It is said that, on this occasion, Kanellopoulos turned to Van Fleet
and said "General, you are witnessing the construction of contemporary
Greece's New Parthenon."

Later on when Van Fleet was retired and visited Greece as a mere
civilian, not a member of any U.S. administration, Kanellopoulos
welcomed him and servilely invited him to inspect "His", Van Fleet's
Army.

Many Thanks.
_nick_at_nite_-ga

Hi _nick_at_nite

Thanks for your message, and all the interesting information. I didn't
know about the camps on Makronisos before; memories of them make sad
reading.

For possible sources of help with your query:

Have you already tried the email link and bibliography at the bottom
of this page?
http://www.faoa.org/journal/vanfleet.html

Or these people?
http://web.otenet.gr/aski/e-main.htm
http://web.otenet.gr/aski/te-all.htm

Or this collection?
http://www.karamanlis-foundation.gr/en/drastiriotites/araanastas.html

Good luck with your research - Leli