We currently have a player who wants to play a Sororita, but he dosent like to play female characters. I dont realy like to bend the lore all to much, and I am currently trying to find another loophole to allow for a male counterpart for the Sororitas, but I cant realy find anything.
Well, if you don't want to break the lore why don't you simply try to find out what your friend likes about the SoB (Sisters of Battle) and then point out what other carrers offer the same choices. SoB are basically humans with a very strong religious bent that wear power armour and carry bolters... If its the gear that attracts your friend that it is easy for several other classes to use it. If it a specific skill or talent several other classes offer them I'm sure... If its the new Fait talent SoBs have access allow the player to buy it with another class as an Elite Advancement (possibly without charging him any extra XP).
If it has to be the SoB specific carrer path... Well, just give a different name. Maybe you can say that he is a cleric with a particular martial bent and that, as an "elite advancement", he trained different skills and that the faith talent is actually miracles granted to him by the Emperor (maybe if the character dies you can even canonize him and have eclesiastic NPCs talk about him in future adventures!