Countdown Timer specific for user

Hello
I have a sales page where the timer reflects 24 hours for the user to make a purchase. The offer is made in an email that belongs to an automation.
It would be great if I can insert a countdown timer into the email and point the contact to the sales page where they can see the timer ticking away. 
The current countdown timer is date specific so this doesn't work for my use case. 
Thanks so much!