Bumping the thread because here I am in Tokyo right now and I've made a discovery.
It totally slipped my mind that Japan still heavily uses fluorescent lighting everywhere and because there's no need to fix what ain't broke a lot of these lights use modern ballasts that still rely on starters. These ballasts support up to 4" 40w tubes which is exactly what I'm after even if the ballasts are rated for 100v 50hz.
New problem: I forgot that in 2015 the Japanese government announced the phaseout of incandescent and fluorescent lighting. It's not that by 2020 they will only have LED products available, it's that they have mandated that ALL lighting unless with exemption will be LED by 2020. The result is that while I can still find starters, sockets and tubes, tubes and the ballasts especially can no longer be imported or manufactured. I combed over akihabara and could not find a store that was still selling ballasts. Either you already had a spare or you were being asked to buy an LED replacement.
I think my only chance here now is if I came across a place that was selling used lamps or ballasts in the next week and a half, otherwise I'm back to googling and hoping.