Yep, definitely a 6x, then. They're only made in subdivisions of .25. Unfortunately my spacebar is 6.25x, so I couldn't give you mine, but I think that you can get 6x spacebars more commonly than 6.5x, at least.
Sorry for not being much help, hopefully someone can point you to a place to buy them. If all else fails, I think that Maxkeyboards sells them.
And I think that you have the same set as me, haha. Is that the Banggood 87-key set?