Maybe try eBay? I've been trying to get a small screw-in replacement bulb for a vintage Big Trak - the hardware and electrical shops don't sell them any longer but I did see some similar on eBay. I need to dig out the toy again and measure the old bulb to see if I can match it on online.
thevintagetoyadvertiser.org 1970s and 80s vintage toy ads and other retro paperworks
imperialgunnery.com Vintage Star Wars action figure weapons and accessories guide