Adobe only sells the current version. There are two current versions; one is Lightroom CC which is available with a creative cloud subscription, the other is Lightroom 6 which is a standalone version. You would have to search websites such as Amazon.com, B & H Photo, Adorama or other such websites and see if they have an upgrade version still available.
An alternative would be for you to download the DNG converter and create digital negative copies which you can open with the Lightroom 2.7. But there have been a lot of changes and improvements since Lightroom 2.7. There is a new process version that is much more effective. It would definitely be worth the investment to upgrade, in my opinion.
You can buy from the following link. After clicking "Buy" change from Full to Upgrade; then select your existing LR product from the drop-down menu and the correct pricing will be displayed. Then simply choose “Add to Cart”
You can upgrade fromLR2 to LR6 for $79 or local currency price.
Thank you both for taking the time to reply to me!
I appreciate your help & the link.