Looks like there are a few places that carry them. Here's an example of some that I found.
[link|https://www.mobilesentrix.com/complete-screw-set-compatible-for-ipad-air-1-ipad-5-2017-ipad-6-2018|iPad Replacement Parts Wholesale|new_window=true]
[link|https://www.ebay.com/itm/175065308919|iPad Air A1474 A1475 /iPad 5 A1822 A1823 /iPad 6 A1893 A1954 Screws Set Full Set 6385519950386|new_window=true]
[link|https://www.wirelesspartsinc.com/ipad22ndgenerationfullscrewset39pcs-2-1-1-1.aspx|for Ipad Air 2018 ( A1893 A1954 ), Full Screw Set|new_window=true]
[link|https://www.injuredgadgets.com/screw-set-for-ipad-air-5-6/|Screw Set for iPad Air / 5 / 6 - Injured Gadgets|new_window=true]