I presume you mean, "all that is available from Mac App Store is the most recent version." Since I had already mentioned that fact in my original post, I assumed that it would be clear that I already understood that the App Store does not provide a solution. Apparently I needed to be more specific. My bad.
What I'm asking is, "Where else can I download Configurator (v1.x) for Yosemite." I accept that you don't know, but I'm still going to try to find a solution.
For the record, I talked to Apple Support about this issue today, and they escalated my case up to a manager who agreed that Apple should provide versions of any Apple software for any system that is currently supported, for as long as that system is supported.
The App Store, as currently configured, fails that test. Yosemite and El Capitan are still supported, yet Configurator 2 (the only version available in the App Store) will not run on either of those systems.
The failure is further compounded by the fact that I have a brand new iPad Pro that I cannot configure to work with secure (encrypted) mail (even though it has that capability, in principle) because the only way of creating that configuration profile is with an Apple utility whose current version will not run on my Mac.
If my system were unsupported, I wouldn't expect Apple to accommodate me. But making a necessary utility unavailable in a currently supported system is unconscionable. And yes...I have made certain that Apple has received that feedback.
My Apple support manager judged my request for access to a Yosemite-compatible version of Configurator to be entirely reasonable. He is going to talk to "someone in engineering" to find out how I can get a copy of version I need. In the meantime, he encouraged me to try to find a copy wherever possible.
So, my question still stands: "Where can I get Configurator for Yosemite?"