A number of editions and translations of Plato's Symposium are available for purchase. (The links provided here are Amazon affiliate links, which means that if you click through and purchase from these links, Amazon pays me a small affiliate fee.)

You can find the Symposium anthologized within collections of Plato's dialogues. Here are a few of those:

• The Collected Dialogues of Plato: Including the Letters, editors Hamilton and Cairns (Princeton University Press)
• Plato Complete Works, editors Cooper and Hutchinson (Hackett)

You can also purchase just the Symposium on its own in a number of editions with different translators

• Plato's Symposium, Gill translation (Penguin Classics)
• Plato's Symposium, Bernadette translation (University of Chicago Press)
• Plato's Symposium, Nehemas translation (Hackett)
• Plato's Symposium, Waterfield translation (Oxford World Classics)
• Plato's Symposium, Howatson translation (Cambridge University Press)
• Plato's Symposium, Griffith translation (Everyman Library)