[pgeorgi]

http://web.archive.org/web/*/http://regexps.srparish.net/src... has a few versions of hackerlab and pika.

hackerlab is also part of tla distributions (since the latter uses the former extensively)

hackerlab contains (some version of) rx.

[apgwoz]

A few of those links lead to actual tarballs, but sadly, the pika one does not. :(