Slightly aghast at the cost of one replacement mirror and wondered if anyone has had any joy in repairing one? As in just replacing the mirror, it's in a steel frame?
Worth try a local glazing shop, many independents do mirrors to size too.
Still wont be cheap as you really can't get away with just std 4mm or 6mm mirror glass.
Try looking on line for acrylic mirrors. They are lightweight, give the same reflective quality as glass and are a fraction of the cost. No idea if there is a size limit though, sorry! I've only used them for bathroom decor.