Miniature Lamp, 1819, 1.0W, T3 1/4, 28V, PK10

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Rulovespilots posted on r/labrats6d

https://www.grainger.com/product/Incandescent-Bulb-Incandescent-2FMP9 found it! The same ones are available on Amazon https://a.co/d/0dbOoe8z