We have gocco-compatible flash lamps available in 4-pack or 12-pack.
These are the kind used by gocco printers before RISO came out with proprietary packaging and distribution. Like the RISO bulbs, these sometimes have a light oxidation on the base. Simply rub tip briskly on wood, paper, tinfoil, or even steel wool until you see a shiny spot. ~ voila! Good to go.