You can find multiple new lawnmower engines available from this website.
I have personally used this site before and there customer service is excellent.
https://briggsbits.co.uk/acatalog/Replacement_Engines_and_Shortblocks_.html
Leave me a comment on my Youtube channel if you can’t find a part. Just post your question on the comments section of any video and I will get back to you.
You can find my channel here https://www.youtube.com/c/MowerMan