Latest version available directly is Creative Alchemy v1.45.19 https://support.creative.com/downloads/DriverDetails.aspx?driverID=100239
Judging by changelog, 1.45.20 is integrated into Sound Blaster AE-7 and Sound Blaster AE-9 driver packages.
P.S. I've just installed their driver packages AECMDMasterInstaller_3.4.72.00.exe and surely C:\Program Files (x86)\Creative\ALchemy folder appeared and dsound.dll there has version 2.4.2.18, like that changelog above says.
P.P.S. If that link https://support.creative.com/downloads/DriverDetails.aspx?driverID=100239 doesn't work for you and shows error page instead, switch country on that page to United Kingdom in low right corner and click link again, it should work then.