Below screen graphite sheet

I didn't have any more luck locating the graphite sheet you're looking for, but I did note that it appears at least one replacement midframe comes with the graphite sheet already attached. Here's a picture showing it.

Of course, you'd need to order one in the right color for your phone; some of them on that site are reasonable (under $25 USD), but a couple are quite a bit more pricey; on the order of $60. Anyway, here's the page; hopefully yours is one of the cheap ones!

Google Pixel 8a Replacement Parts – SOULTZ PHONE PARTS

If you do a search for "google Pixel 8a midframe replacement" you'll find a few choices; the one I linked to appears to be an aftermarket replacement. It seems the genuine Google midframes don't come with the graphite sheet. Another option might be to purchase a system pull; i.e., one from a phone that's been parted out; that'll save you some effort on the replacement since it comes with many of the small parts already attached. Here's an example from eBay (again, I don't know what color yours is, so I can't tell if it's the right one for you or not).

Repair Part - OEM Pull Frame with Small Parts for Google Pixel 8A - Obsidian - eBay

You can see from the second picture on the site that the graphite sheet is there and intact, so that might be another option. I'd go with one of those first before trying to make one myself, especially with that oddball little flap that goes over the screen connector.

Good luck, and be sure to come on back and let us know how it all turns out; what you learn will help the next person who comes along with the same problem.