A friend yesterday was saying that she wished she'd never parted with her Haldane Lewis wheel.
Woodlands Turney can make Haldane bobbins to order. They may ask for (one of) your existing bobbin(s) as a pattern; I think I've heard Joan say that there are variations, even between wheels of the same type. Or I may have dreamed that.
It might be worth asking them if they could make a jumbo flyer for your Lewis.
Orkneys do come up on eBay from time to time; one sold quite recently actually. The sellers don't always know what they've got, of course.

Edited to remove unintended crossing out!