That is the plastic fairing around the air filter opening in the cowling. The last three digits now added following the original part number (-279) is the color code (black, in this case). Color doesn't matter, as it will likely be painted to match the cowling anyway.
Still available new from Cessna, but as noted, any new Cessna part is outrageous in price. Used parts are available at sometimes huge discounts, but no two identical parts will have the same rivet hole alignment (even if they are removed without further damage). Most small aircraft (including Cessnas) use a minimum of pre-drilled alignment holes, with the rest drilled by hand. Used parts often require oversized rivets to gain proper hole alignment.
Google "aircraft salvage" to obtain listings containing sources for used parts. There are many, probably some local to you. Also check Ebay.... which never ceases to amaze me as a parts source.