Find an old tablet that's selling for like 50 bucks, and it should work, but don't sue me. Maybe ask the seller to install the app and see if it works?
Most life total apps aren't especially life-draining or lag-causing. The vast majority of battery that gets drained by a device is used by the screen, so turn down the brightness and it'll live longer. If it's the only thing you're using on it, starting at 100% battery, it should last several hours, especially if you have the brightness down and airplane mode on so it's not wasting battery sending and receiving wifi and roaming signals.
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"Life is a joke. Yours, mine, everyone's."
—Tyrion Lannister, A Dance with Dragons