Straight dust covers aren't super common anymore on 92fs. They do show up time to time and are likely in my opinion the result of sharing parts with the M9 or Italian made parts. It seems like during shortages or huge demands (Sandy Hook, Biden election, summer riots) that you see this happening.
Slides are a dime a dozen, you can buy new ones on Ebay really cheap. The straight dust cover is the harder thing to find if that's what you are looking for.