Replacing just the glass cover on your display assembly is a difficult task. If you have not already, take a look at this guide. The procedure for removing the display assembly from the computer will be different on a MacBook Pro 13" mid 2012, but the procedure for separating the front glass is the same. iFixit doesn't sell the front glass or the adhesive anymore. A quick internet search for "MacBook Pro 13 display glass" turned up several sources, and some of them, have adhesive included. It is very unlikely that the old adhesive will be in any shape to reuse when you get the old glass off. It is an easier but far more expensive repair to replace the whole display assembly. Replacing just the glass requires tons of patience removing the broken pieces and all the left over adhesive, and the result may not be aesthetically pleasing. Getting it all back together like the original assembly with no lumps can be challenging. Good luck on your repair!