how to locate a 16gb ipad charger

You question needs clarification.

“16GB” suggests storage capacity - which is obviously irrelevant for any charging solution.

If you describe exactly what you are attempting to achieve - which may also require you to provide information about your iPad model and installed version of iOS/iPadOS - contributors might be better able to provide appropriate help or guidance.

If all you’re looking for is a power adaptor, this model will meet the power requirements of any iPad:

https://store.apple.com/xc/product/MHJA3AM/A