The iPad 2 is an old device; there are no more OEM parts available. Anything you buy "new" will be aftermarket. That said, there are still great quality digitizers out there if you buy from reputable vendors.
If you want an "original" you will have to buy used parts. A-grade / B-grade just tells you how good they look. A-grade should be in excellent condition but a B-grade will probably have some minor scratches.
Contact iFixit Support (help.ifixit.com) to find out, we are just volunteers here helping out DIY fixers.