The part number is usually stamped on the inside of the bumper or on a sticker, but it can be tough to spot.The part number isn't usually stamped directly on the bumper itself where it's easily visible, so you'll have to pull up a parts diagram specific to your year, make and model.
It should be much easier to check with dealerships or online OEM parts websites by inputting your VIN!
For shops, check out sites like RockAuto.com, PartsGeek.com, or eBay.
They have good options for both aftermarket or used OEM bumpers!