MySQL 5.5 on Debian 9 (stretch) can't find libssl1.0.0

I am trying to install MySQL 5.5 (has to be that version, unfortunately) on a freshly installed Debian 9 system, and there is one dependency that I can’t easily fix, it seems:

dpkg: dependency problems prevent configuration of percona-server-server-5.5:
percona-server-server-5.5 depends on percona-server-client-5.5 (>= 5.5.44-rel37.3-1.jessie); however:
Package percona-server-client-5.5 is not configured yet.
percona-server-server-5.5 depends on libdbd-mysql-perl; however:
Package libdbd-mysql-perl is not installed.
percona-server-server-5.5 depends on libaio1 (>= 0.3.93); however:
Package libaio1 is not installed.
percona-server-server-5.5 depends on libssl1.0.0 (>= 1.0.0); however:
Package libssl1.0.0 is not installed.

However, this package is no longer available, apparently:

root@ip-10-0-1-64:~/mysql# dpkg-query -l 'libssl*'
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description
un libssl1.0.0 <none> <none> (no description available)
ii libssl1.0.2:amd64 1.0.2s-1~deb9u1 amd64 Secure Sockets Layer toolkit - shared libraries
ii libssl1.1:amd64 1.1.0k-1~deb9u1 amd64 Secure Sockets Layer toolkit - shared libraries

Is there a way to fix this?

The solution to this problem turns out to be to add something extra to the apt source list - this isn’t mentioned in the official documentation, as far as I can see:

# install percona for mysql 5.5
/usr/bin/dpkg -i *deb
cat > /etc/apt/sources.list.d/percona.list <<!
deb stretch main
deb-src stretch main
/usr/bin/apt-get update
DEBIAN_FRONTEND=noninteractive /usr/bin/apt-get -q -y install percona-server-server-5.5
/usr/bin/percona-release enable-only tools release
/usr/bin/apt-get update
DEBIAN_FRONTEND=noninteractive /usr/bin/apt-get -q -y install percona-xtrabackup-24