Add a One-Time Order to a Current Product Subscription.
If you want to add a one-time order to a current product subscription.
Go to My Account.
Click on Subscriptions.
Click 'View Details' for the subscription you would like to edit.
Click 'Add Product to Subscription'.
Click 'Add as One-Time Order' to add product to current subscription.
Once all desired products are added to your cart, click 'Save'.
One-time order will be shown at checkout on your subscription order.