adding more insulation on garage side of wall, and held in place with plastic sheeting has resulted in a moisture issue
Yes, you caused the problem by putting plastic (vapor barrier) on the cold side of the insulation (and having two vapor barriers in the wall.)
You can use mesh nets (commonly intended for holding cellulose insulation.) You could use housewrap, in theory, anyway - its an air but not vapor barrier, that's the whole point of house wrap.