All dashes are the same. The P/N might have changed slightly due to minor updates.
Here is a brand new dash on eBay for about $400 shipped.https://www.ebay.com/itm/New-OEM-Lexus-IS250-Front-Bare-Dash-Panel-Dashboard-Black-5540053906C0/142427025707

 

Out of nowhere otherwise mint dash developed a nasty crack recently, no melting. New 400 shipped seems good deal. I have to change it myself, dealer wants 1400.

 

Update. ebay 400 shipped dash is actually an 800 shipped dash. after you pay, they claim that the dimension of the item are too large. Still have not received my 400 back.
Dealer offered a deal 850 with install, im going to take it.
55400-53909-C0 is the correct and the latest part number.