What types of 3rd party adapters and cables has anyone found for usb-c charging IPad Air 4?

There are many compatible third-party Power Adapters and cables for iPad and the Air4. What is perhaps most important, if contemplating a non-Apple Power Adapter or charging cable, is that you choose a reputable manufacturer of good quality.

Given the relatively high cost of your iPad, choosing a cheap alternative Power Adapter or cable is false economy - as any damage that you cause to your iPad will not be covered by your warranty - and any warranty provided by the manufacturer of the Power Adapter (if there is any warranty at all) will not cover consequential damage to the device to which it was connected.

Cables are also an area in which to be careful - as defective or broken cables can cause significant damage to both iPad and Power Adapter.

Of third-party Power Adapters, always choose a well known brand of good reputation and quality. A good indicator of reliability and quality, for third-party charging products, might be Apple’s own online Store. If the third-party manufacturer’s product is actually marketed by Apple, then it meets Apple’s quality standards and compatibility requirements. You can of course buy from a different source, but be aware that counterfeit goods are commonplace.

Anker, Mophie (Zagg) and Belkin are well regarded alternatives to Apple, for both Power Adapters and cables.