Does the oven door need to be toughened glass?

I'm going to say, "yes", there is a reason that oven glass needs to be able to stand up to the heat. Even for a toaster oven. Safety. What Kind of Glass is Used in Oven Doors

The online order/quote for tempered glass I pulled up, guessing a 8"x12" sheet, quoted at $60 (plus taxes/shipping). Then you have to take into consideration: the glass for your specific toaster oven might have (pre-drilled) holes for a handle to be screwed on, or adjustments for the bolts that fit it so that it swings open. Perhaps you could get a replacement part by contacting the manufacturer (if the appliance isn't too old).

But it might not be worth your while to go through all that trouble. Check local discount shops (or even garage sales). I bet you could replace or upgrade the appliance for less money and aggrivation that fixing it would cause.