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What of adding some LH studs w/ LH nuts as these currently on eBoy...
https://www.ebay.com/itm/16407326247...MAAOSwubdePxjR
Even if temporary 'til you find more, only you'd know plus it could help thwart theft too?
Also, if OSD of 7/16" and 1/2" the same, could you retap 7/16" LH to 1/2" RH?

Even tapping 1/2" LH to 1/2" RH may work also if weaker, one @ each wheel Ok?
Best of luck w/ your quest!

~ Pete
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