I spotted your new thread about E21a - I know you’re desperate for 10440s but I suspect a 10440 resistor “driven” light would actually have less runtime than one with a boost circuit and AAA NiMh…
While you’re looking to get involved with some modding, how about an E3A resistor mod to tide you over until you get the Solitaire project sorted? It runs on AAA but you can choose output/runtime by the resistor you select.