Do I understand you to say you may change the floral scent in your book? If so, choose one that is easier to come by. Lily of the Valley FO by Nature's Garden is not overly expensive and a lovely scent. I don't know how it would pair with vanilla, but I have used and enjoyed it on its own. That is if you are open to using FOs.
If it is only EOs you want to use and you want to evaluate an EO in person, might I suggest you go into a brick and mortar store and do some sniff testing to get an idea of which EOs might be of interest. One place where this works very well is The Vitamin Shoppe, where you can do sniff tests and they keep fresh coffee beans to sniff between sniffing scents to 'clear the nasal palette'. There may be other stores near where you live that provide a similar sniff-testing opportunity. It just the only one near where I live where I have found I can do that. I think some Whole Foods Stores also let you sniff, but I don't recall ever seeing the coffee beans to clear the nasal palette. But you could carry a small container of coffee beans with you.
I suggest this because if you find something you like, you would actually get an idea of cost. It may actually cost more at one of these stores than you if you order from Nature's Garden or Bramble Berry, etc. But you would be able to see the trend of higher and lower costs of what they have in stock and get a better idea if something goes well with vanilla, since vanilla seems to be part of what you want as well. Although I can't imagine a floral scent that would not go well with vanilla.