Corsair Spec-02 doesn't have partial tempered glass side panel. What it does have is acrylic window.
As said above, jerry-rigging TG side panel to a case that doesn't have one most likely costs more than a new case that already has TG side panel in stock. Not to mention all the time and work needed to spend getting TG side panel for Spec-02.
Here, i too suggest getting a new case with TG side panel but since choosing a PC case is personal choice, go with the one that you like the most. I can only give you additional suggestions regarding cases with tempered glass side panel, like:
Note: In brackets, ( ), is CPU cooler clearance.
Corsair lineup:
Spec-04 TG, (150mm)...