I've attached the media I've been able to find regarding this singular bolt that seems to be eluding me.

I've located this part number but I'm not 100% sure if it's it: 90119-16021 https://www.monotaro.com/p/2654/9942/
I'm pretty sure it is different from the ISF part number which is 90119-16013

I've beat my head against the wall with this for 5 or 6 hours at this point and have just been running in circles with it. Any help would be greatly apprecaited.

 

I hope what you looking for is listed in the following link.
https://www.lexuspartsnow.com/parts-...tml?pnc=43330M
Like you mentioned, hard to find that exact part number. It seems like it's a 22mm bolt with a washer.

 

It's part number 90119-16021. If you click 'view more images', its in the second diagram.

https://parts.belllexusnorthscottsda...102.html#51201

 

I came up with that same part number as well. On the SUSPENSION CROSSMEMBER & UNDER COVER page, specifically it's the bolt shown that goes into the rear of the front subframe. You have to follow the dotted line a bit because it shows that bolt going thru a chassis brace also.

Specs want that thing torqued to 143 ft/lbs, so it has a lot of forces applied to it.