My lecky fit me in in short notice, give them a call (Jenkins autospark in myaree).Our plastic box has done over 20,000 kms so far and the only attrition, so far, is the straps I used to make sure the lid didn't come off. The straps have disintegrated and will be replaced.
The good thing is that the box itself weighs 4kgs with some stuff in it...not the weber, just incidental bits...which is a hell of a lot lighter than a big metal toolbox.
Just not as sturdy or as secure....but a 10 year old weber doesn't need that.
You are certainly making progress with all the mods.....good on you.
Want to do an Anderson for me? My auto leckie is flat strap and can't do it for another week.
Our placky box won't be as robust as yours. I'll just grab one of the ones I keep the kids toys in for this trip and see how it goes.