Unfortunately, Bramley Seedlings aren’t widely available in the US. There is an orchard near me which grows a number of heirloom varietals and I have purchased Bramleys there - they do make a great pie! Ditto Newtown Pippin - I have only seen them at specific orchards that specialize in heirloom varietals.
Most of my local orchards now grow Northern Spies, which are great for pie, but they seem to sell out quickly in season. When I can find them, I like to use at least half Spies with maybe a Golden Delicious and a McIntosh mixed in, but even an all-Spy pie is pretty darn good.
If I’m using supermarket apples for pie, I usually use equal parts Granny Smith, Golden Delicious, McIntosh and something else - that something else is whatever the store has. Galas, Pink Lady, Jonagold, Empire - they all bring something to the party. If none of those varieties looks good then I just go Granny/Golden/Mac. I like this combo because I like my apple pies to have both intact slices of apple AND lots of apple goo, plus a good sweet-tart balance. McIntosh apples break down almost entirely into luscious goo, while Goldens and especially Grannys stay more intact. I always slice the Grannys much more thinly than other varieties because they are SO crisp. The Goldens bring the sweet while the Grannys provide the tart.