How can I buy online a train ticket from Reading to London which also includes a one day London Travel Card?

I need to travel from Reading to London tomorrow and need to use a lot of the tubes whilst in London and a friend told me that it is possible to buy an all in one ticket that includes all of this but I can't find this anywhere on the train ticket websites, help please? thank you in advance

I think you are better off just buying from the station.
I usually get this and it costs about £18.
I just checked the first great western website and it costs about £39!

You can buy a single ticket and an all day railcard for £19.20 on this site.
www.nationalexpresseastcoast.com