Yes! Even though Coding Duo is listed as part of the 'Coding Family' on the Playosmo website, you may purchase it separately. Simply:
1- click on the 'Coding Family' item
2- check off the boxes for Coding Awbie and Coding Jam (which indicate that you already have those games and their game pieces), and you will be able to checkout with just Coding Duo in the shopping cart.
Note that in order to play Coding Duo, you NEED the Coding Awbie AND Coding Jam game pieces too.
Coding Duo is sold exclusively on the Playosmo website, and not via any retail partner.