Yup, select First/Business in the pull down list then search for your flight.
x-UP will appear as A or D fares for domestic first/business. You can verify what the fare class it by selecting the flights and when you get the page that shows your trip summary before clicking on review and purchase, click on the 'View change & cancellation policies"
For example, on your flights there are M-UP fares available that book into A.