Rebuilding a car is an ambitious undertaking! Good for you.
The second place you can buy a 2007 Toyota Camry 2.4 engine is secondhand through an online store. EBay and local platforms like OfferUp and Craiglist often have full engines available from people parting out their cars. You will have to conduct your own inspection to make sure the engine meets your requirements.
Lastly, check with a local junkyard. You may be able to find a 2007 Toyota Camry 2.4 engine sitting in an unused Camry and buy it. Like the previous option, it’s best to use this option only if you know how to inspect the engine yourself.