I had the same issue with my old microwave a few months ago! I searched everywhere online and couldn’t find the right wave guide either. I ended up reaching out to the team at vanproappliance.ca since they’d helped me with a fridge repair before. They were super helpful.
Visit site for more details. They didn’t have the exact part in stock, but they tracked it down for me and even walked me through how to install it over the phone so I didn’t mess anything up. Saved me a lot of time and frustration, and I didn’t have to buy a new microwave.