For real, that box is phenomenal bro!!

So, turns out my idler pulley 'washer' and bolt are randomly missing. A buddy of mine changed it for me back over the summer. I don't know if he forgot to put it in months ago or it fell out randomly or what, but I don't want to drive the car without it (although I probably have been for.... i have no idea how long). Best place to figure out what the correct bolt is? Probably an online Honda parts store, I just want to confirm that it's the right bolt/washer