Hi niedermee.
Your Apollo came out of the Fujigen Gakki factory in the later 1960's. Finding a neck will be tough but not impossible. Many Fujigen guitars were imported into the US. The most popular brand name used on these imports was Greco, but they were also sold as Apollo, Sekova, Domino, Encore, Merlin, Fiama and Heit just to name a few. The laminate neck construction started in 1967 so you are looking for a late 60's-early 70's neck. You probably will not find an exact match for your fender style headstock shape since most of the Fujigen hollow bodies used 3 on side tuners.
Be prepared for a long search, there are a lot more bodies than necks out in the market.
I have a suggestion assuming you have no emotional attachment to this particular instrument. Consider parting out the body you have and using the money to buy an intact Fujigen built hollow body. The parts used on your guitar should be in demand since many similar instruments still exist. Generally, these 60's Japanese imports are worth more in parts than intact instruments so you might be money ahead to salvage whatever value you can out of the body and shop for a different guitar.
good luck with your search, sometimes a fish bites on the first cast