good molecular builder



 Hello.
 
Could anyone suggest a convenient molecular builder. My task is, say, I have optimized geometry for water and nitric anion. Then I want to compose a system using their geometries with cation, anion and 10 waters.
 It is enough if it saves xyz file. In fact it is preferably.
 
Any suggestions? Everything I saw either shows molecules or offer building but from the very scratch.
 Thank you all in advance.
 Regards.
 	---Dmitry.