Does anyone happen to have a save file for new game plus runs available?

I think it's not possible, I try to load a save from a friend and the game thank it was corrupt.

And for my confort, I tried to get one save for the speedrun and on save with all my stuff and it seems to bug the game. In the hydra fight in the encampment , I can't one shot the hydra, I need to wait after it destroy the tower before kill it, so about 45s time lost.

You should complete the game and farm all the item yourself to speedrun the game, it's the better and safer option I think.