Think you just need something like these: https://www.ebay.co.uk/itm/144475400427
Cheers.
I guess being too wide for the bars doesn't matter as it'll be clamped(?)
And it just needs to be long enough for the threads, reach through the box and round the bars.
@hugo7 started
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Think you just need something like these:
https://www.ebay.co.uk/itm/144475400427