With the possible exception of certain 'Megatrain' fares (which only apply to some rail services operated by the Stagecoach group) every available rail fare should always be shown on the National Rail website:
http://www.nationalrail.co.uk/
Using any other site is pointless (because they can't offer any better fares), sometimes costly (because some sites charge a booking fee) and possibly risky. (I used to run a railway station; I've seen plenty of tickets issued by sites like the Trainline.com which simply weren't valid for travel on ANY train!)
Since Megatrain don't serve Bradford (or anywhere close, like Leeds), just use the National Rail site. I've just entered a couple of random dates (out on Sunday 15/08, back the following Sunday) and I've been offered £21 in each direction. £42 return compares well with the normal (lower) off-peak return fare of £84.70 or the full return fare of £228.00.
Chris