Need a checklist for your airplane? Dauntless curates a collection of user-provided checklists for many airplanes.
You can find the collection here.
However, be sure to check that the checklist you use is appropriate for the airplane you are flying. While many Commercial Off-the-Shelf (COTS) checklists can apply to the majority of stock, fresh-off-the-factory-floor, like-kind make/model airplanes, there may be additional equipment or aftermarket modifications that would make the checklist incomplete or the V-speeds different from another similar airplane.
You can also use these as a basis along with the POH/AFM to create your own checklist. There are many great examples with both normal and emergency procedures to choose from.
There is no approval required from the FAA to modify or customize a checklist and the FAA released a Safety Alert for Operators (SAFO 17006) in 2017 that addresses safety concerns with using commercial off-the-shelf (COTS) or personally developed checklists. Here is the LINK to that SAFO.
If you choose to use another’s checklist (or create your own), it is important to refer back to the POH/AFM of the airplane you are flying and any applicable STCs that may have been implemented over the years to ensure nothing is missed (e.g. a STOL kit), the procedures on the checklist reflect what the manufacturer specifies, and meet the needs for a safe flight.