Called Breville - they DO NOT sell parts to anyone. That includes websites like Fixit.com and others. The only place to get the exact Breville spring for your oven (mine is a B0V800XL) is to send it to the repair center in Torrance, CA. You pay for shipping, both ways, and the repair is not cheap.
If you are able to find a junked Breville, same model as yours, on eBay or Craigs List, then go that route. Otherwise, either pay the big bucks to send it to Breville - Torrance for repair, or buy a new oven for $240.
Sorry for the bad news.