https://old.reddit.com/r/typewriters/comments/1h4b3aw/is_there_a_source_that_exists_that_sells_or/

If you need them for basic functionality, often you can find the manuals of the original manufacturers' models for rebrands (example: the Sears Tower machines which were really just rebrandings of the Smith-Corona 5 series).

Additionally, after the 1930s there really wasn't a lot of new functionality, so almost any manual will help you to get you where you need to go, though there are some small differences in locations of things like carriage locks which can be helpful to know about and whose placement moved around on various machines.

You might also notice that as typewriters were more ubiquitous in the 60s and 70s their manuals got thinner and thinner with less detail. If you do find a specific manual, you're unlikely to find very much in it.

The Davis Brothers have some history on the Commodore line which was related to some of the Sears Chevron line. Polt does have two Commodore manuals which may be close to your machine: https://site.xavier.edu/polt/typewriters/tw-manuals.html