Would you not be able to download the certificate a second time, you may want to simply copy your Keychain — or the key pair — from your work machine. You will be able to import the file on your home machine.
Your keychains are stored in :
[Home] -> Library -> Keychains
© 2015, O’Reilly Media, Inc.
All trademarks and registered trademarks appearing on oreilly.com are the property of their respective owners.