Legitimate source for purchasing Captivate 9?

Hello. My client is using Captivate 9 so subscribing to Captivate 2017 isn't feasible for me because my client won't be able to open my files. So I think i need to purchase Captivate 9 to work with her. Can anyone recommend a legitimate source for purchasing it? I see a lot of offers online but some seem a bit shady and since this is for corporate work, I want to be sure I have a legitimate version. Thanks.