This is the book I use to find the genus of unknown plants - covers all flowering plants in the world....published in 1965 , I show the 1989 reprint - likely to be still in print I think. Not too expensive I expect , mine was the equivalant of about US$ 12 when I bought it.
Pity we are not nearer , you could pop round and borrow it... !
I use it very occasionally, and generally find that once I have the genus, I can find some kind of guide which leads me to the species more easily - I say that since a certain amount of botanical expertise, with a lot of unfamiliar terms, is needed to use the book although there is a glossary, or I use the Oxford Dictionary of Life sciences words ( or some such title) when needed.
Actually the flower looks quite familiar, and similar to a white flowered dangling plant I grow in my greenhouse - the leaves look much the same too - unfortunately it has lost its name tag, and it won't be in flower again until next summer for me to do a count on corolla parts, stamens etc etc to use the one I illustrate.
The best of luck with your search .