For $29/mo, we provide access to advanced level technicians who will answer your questions on any Macbook board related matter to the best of their knowledge promptly & walk you through how to solve your problem so you can deliver a working board to your customer.
I have not been able to buy that since 2015. I stocked up on 300 of them and used them all up a long time ago. Now you are pretty much stuck looking for used assemblies. Always remember to make sure your customer knows why you are limited in your options to help them, how the manufacturer uses non-standard parts and tries their best to make them unavailable to you.