Wrapping up my head gasket job and realized I've lost the fancy washer that goes with the single 10mm bolt that goes into the valve cover gasket. Apparently this is a guaranteed significant oil leak so I need to replace it correctly, and probably from the stealership. I haven't been able to find a part number for this anywhere. The part is labeled "SEAL WASHER" in the attached diagram. Any help would be greatly appreciated.
Fair warning to those contemplating this work: I was also unable to find locally (beyond the Toyota place full of sales schmucks which I detest) the timing chain tensioner gasket, which had already started to seep, and the camshaft bearing cap oil hole gasket which looks like graffiti drawn by teenagers in a bathroom - if you know the one I'm talking about you know what I mean
The seal washer has Toyota part number 16258-37010, list price $5.46. See parts catalog Figure 11-06, Timing Gear Cover & Rear End Plate. For future reference, parts shown with the ● symbol in the diagrams are considered non-reusable; even if you hadn’t lost the old seal, you should use a new one when reinstalling the bolt.
"Seal Washer" might be item 3 here, part no Timing gear cover & rear end plate for Toyota Prius 3 generation, restyling 12.2011 - 11.2015 - Toyota Car & Auto Spare Parts - Genuine Online Car Parts Catalogue - Amayama Specifically: Buy Genuine Toyota 1625837010 (16258-37010) Gasket. Prices, fast shipping, photos, weight - Amayama (Hah, @Elektroingenieur beat me to it)
