> Any workarround?
For the records, yes, a tricky one, using the libbaselinks module to rewrite
links. However, it is strongly advised to dramatically reduce the number of
connections (one connection each 10 seconds for example), not to stress the
archive site, which is often overloaded.

Example:
httrack --sockets=1 --connection-per-second=0.1 \
    --wrapper
'/usr/lib/httrack/libtest/libbaselinks.so.1.0.0,http://web.archive.org/web/THE_DATE/
\
<http://web.archive.org/web/THE_DATE/http://example.com/index.html> \
    -* +web.archive.org/web/THE_DATE/http://example.com/*.html

(beware not to allow everything under web/ or you'll download the entire
archive)