Craft an Unfired Clay Bucket from three pieces of clay and then smelt that bucket to get a Clay Bucket. A Clay Bucket can hold water and lava but will crumble in your hands once you've poured lava out.
Now you might be saying: "But abecderic, I already have a clay bucket! Iguanas Tinker Tweaks adds one." If you have Iguanas Tinker Tweaks then this mod is not for you. But if you don't have it and want a clay bucket... well, here you go.
You can use Clay Bucket in your modpack, but monetization is not allowed.