Ebay and Amazon are always great resources to find OEM controllers. Usually when you search for them, there are filters on the left side which you can use to filter out knock off brands. Just select Nintendo as your brand and always look to see where the product is shipping from. I usually never trust sellers from China, and you can also filter by location as well to avoid this.
As for sensor bars, a simple knock off USB sensor bar is all you need, really. The sensor bar is just a set of IR lights used by the Wiimote. I bought a generic sensor bar from amazon that is connected to my TV and I haven't had any issues with it, and I've mostly been playing Sin and Punishment: Star Successor for aiming.
https://www.amazon.com/Best-Deal%E3%80%91OriGlam-Wii-Sensor-Bar-Replacement/dp/B01NBC8BHI/ref=sr_1_3?keywords=usb+sensor+bar&qid=1554249988&s=gateway&sr=8-3
As for sensor bars, a simple knock off USB sensor bar is all you need, really. The sensor bar is just a set of IR lights used by the Wiimote. I bought a generic sensor bar from amazon that is connected to my TV and I haven't had any issues with it, and I've mostly been playing Sin and Punishment: Star Successor for aiming.
https://www.amazon.com/Best-Deal%E3%80%91OriGlam-Wii-Sensor-Bar-Replacement/dp/B01NBC8BHI/ref=sr_1_3?keywords=usb+sensor+bar&qid=1554249988&s=gateway&sr=8-3