I would just look in a few books on Henry VII (try your local library) and use the index to refer to foreign policy and see if you can find any quotes which support that Henry VII's foreign policy was something other than defensive (it'll probably be financial gain, perhaps evident in the Treaty of Étaples and the pension received from that). A great bio on Henry VII is Penn's Winter King but I am not sure what he argued on this, I have read the book though and highlighted some bits so I can check if you would like.
For foreign policy sources, I would look within biographies, e.g. one on Mary I for her foreign policy, and they often have quotes. Do you need the source to cover a particular monarch? You could always consider Elizabeth I's Tilbury Speech if you want to do a speech. Or possibly you could do Mary I's speech in London against Wyatt Rebellion (and link it back in with the English reaction to the Spanish marriage and that area of foreign policy).
Otherwise, I would advise that you consider another type of source, like an ambassador's report (this could be difficult though if you cannot use a letter again) or perhaps a chronicle, like Hall's Chronicle, or The chronicle of Queen Jane, and of two years of Queen Mary, or something like John Foxe's Book of Martyrs will probably reference Mary I's Spanish and French foreign policy. You can find these sources online.