Yes, you'll need to get the guides direct from
Prima Games if you can't track one down in the stores. You can either order hard-copy versions of guides from them, or download PDF versions of the guides if waiting for hard-copy versions is too much of a hassle for you. Either way, they cost money, and getting a PDF version is cheaper obviously.
I had trouble tracking down the Bon Voyage guide, so eventually my lack of patience got the better of me and I downloaded the PDF version, which costs about $15 in US currency, if I remember correctly.
If ordering stuff isn't an option, then you might be lucky to find guide snippets and relevant info posted here and there at different sites.