I'll just stop you right there a second.
Not practical?
Ansible 2 was released nearly 2 years ago.
There's not that much work to port 1.9 code over and there's substantial gains from using a 2+ codebase.
You really should be doing some automated testing of your ansible code, even if it's just a syntax check and lint to pick up deprecation.
Do keep in mind the controlling system is the only one where the version of ansible matters... you don't need to screw around with your repo config on target systems.
The best place to get a package no longer in the current repo is koji rather than trying to dig out a mirror that hasn't replicated in over a year.
For future reference, it's worth having your preferred CI (Jenkins or gitlab etc) use nightlies (docker container makes this trivial) run a syntax check against your playbooks to avoid this happening again.
Upstream provides rpms to make this simple.