You only get one bonus action per turn and you cannot use your action to do something that takes a bonus action. There are no spells, feats, or class features that can bypass this restriction.
With find familiar and a ring of spell storing, probably
If you have the find familiar spell (PHB, p. 240) and a ring of spell storing (DMG, p. 192), your familiar can attune to and use the ring. You just need to cast the hex spell into the ring before combat, and then the familiar can cast it for you in the same round that you use Hexblade's Curse. As written, the familiar "rolls its own initiative and acts on its own turn", but most DMs I have played with prefer to let it act on your turn.
This is somewhat up to DM discretion, as it isn't clear if an owl or lizard can wear a ring (but an octopus probably can). If this becomes a problem, ask your DM if any of the special familiars - imp, pseudodragon, quasit, or sprite - granted by Pact of the Chain (PHB, p. 107) would work.
As a Thief Rogue 17 / Hexblade 1, yes
When you reach 17th level, you have become adept at laying ambushes and quickly escaping danger. You can take two turns during the first round of any combat. You take your first turn at your normal initiative and your second turn at your initiative minus 10. You can't use this feature when you are surprised.
PHB, p. 97, emphasis mine
This 17th-level Thief Rogue ability will allow you to use two bonus actions in the same round (though not in the same turn).