I am struggling to find one and didn't expect mine to be so thrashed.
I am without car right now so would greatly appreciate if someone can bring one by, thanks!

18mm? What on earth are you using this for....hydraulic lines on an excavator? That's HUGE.

That the size of the tranny drain crush washer

Just looked, I guess it is. I don't recall it being that big...feel like I've been losing my mind today.

wrap the threads in teflon it will hold till you find one. You can even put some rtv under the head flange of the bolt it is hillbilly but it will get you on the road.

So I guess the fact that the replacement ones at CT come with plastic washers isn't really an issue?

If you have a plastic one that will be fine. You just cant tighten it as much. I like the aluminum crashed washer better, but the plastic will work.

Cool, thanks Stephen!

Pretty sure I stocked up on 4-5 of every crush washer from Ziggy.

If he can't help you, I probably can.

I've used the plastic CT ones and have never had an issue I've even had to reuse a couple and they still work like new. NO JUDGING!

Cool, that's what I wanted to hear Johnny, thanks!!

I am going to pick up copper ones tomorrow at CT, was actually able to find them local so that's good.

You know which ones I really like and have had excellent success with? The ones that are aluminum outer rings with a rubber inner ring.

It looks like the one on the left:

That's fancy, where do you get those?

Parts Source is where I get 'em, but I'm sure any part store will have them and probably even Crappy Tire.