There’s not much of a choice, as google reveals.
Most offers are SK68 clones, they are cheap but have an abysmal beam profile.
Next problem is, that with flashlights red often isn’t red (like in Maglite Mini Cool Dark Red) but more of a pink color.
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Best one for ages was a host that cnqualitygoods sold.
B1 1xAA Red Shell Flashlight Host Kit
Some assembly required 
But afaik it’s not sold anymore.
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Best thing I can come up with is the Solarforce Z2, which comes in some kind of red as well.
