@Kev75 NOW TV have their own gift card page here
codes are purchased via PayPal Gifts and delivered by email.
If you're interested in a one-month sports pass you're better off getting it from Currys (physical card delivered or picked up in store) tho as they are £25 compared to £34 on NOW TV
NOW TV have changed their pricing for the bundles with devices so if you're looking for cheap passes buying a device bundle isn't usually the best way to go now, although you may find better deals around bank holidays and Christmas time.
Keeping an eye on discount sharing websites like HotUKDeals is usually the best way to look for bargains.