I’m going to answer my own question (weeks after I posted it). The Percona APT repositories do include distributions for Ubuntu Oneiric, even though it’s not listed on http://www.percona.com/doc/percona-server/5.5/installation/a pt_repo.html). When running Oneiric, simply add the following to /etc/apt/sources.list
deb [URL]http://repo.percona.com/apt[/URL] oneiric main
deb-src [URL]http://repo.percona.com/apt[/URL] oneiric main
and follow the directions shown on http://www.percona.com/doc/percona-server/5.5/installation/a pt_repo.html
Works perfectly!