Side steps OEM - solution for a missing mounting part

I obtained used Jimny 3 OEM plastic side steps.

Part number could either be 99000-990YB-776, 99000-990YB-777 or 99000-990YB-715 (they all look the same).

I attached pictures of the side steps.


The problem is that I now realized that I got all the mounting hardware except some very special big thick bolts&nuts which go into existing large holes in the chassis itself.
It appears that those bolts&nuts are rarely sold alongside used side steps on the second hand market, probably because they get seized by the time a used side step is being removed after all those years .....


Unfortunately, I can not ask the seller to resend those to me as the vehicle has been scrapped in the meantime.


Now I need either to:
1. Obtain the missing parts from somewhere else;
2. Fabricate replicas based on some specifications or measurements given by others;
3. Improvise some other way to securely mount the side steps to the chassis.


I found the pictures of the missing parts on the Internet, and I will post them in a follow-up reply to this message (to avoid confusing images).

Here are attached some Internet pictures of the missing special thick nuts&bolts.
I circled the missing parts in red in each picture.


I would highly appreciate help on this matter because these side steps weren't cheap to obtain (expensive postage) and I had no clue that these missing parts even existed until a thorough Internet picture search ...

It appears that these missing parts are common for any model of OEM side steps.

Ah yes the infamous spreading sleeves. Your best bet is to find someone with a lathe and make some to fit your car.

That is one of the options.

But I need some measurements or drawings to begin with. Could someone remove one OEM side step from their Jimny and take some measurement of this bolt and sleeve for me?

That would be an excellent opportunity for them to coat the bolts with some anti-seize compound for future removal.

I assume said rawbolt fits into one of the chassis cross tubes, if so can't you just measure the chassis tube?
Give yourself a.5mm clearance to allow it to slide in, looks to be about 40mm deep, but I doubt it needs to be super accurate and the bolt is the biggest that will fit the hole in the side step bracket.
Alternatively weld a plate over the chassis tube with a nut welded centrally on the inside of side plate, instant captive support bolt point.
Sorry if it's more complex than this.
Only trying to help.

Like Scimike says the necessary dimensions are easily measured from the step and chassis and if your engineer has a picture of the expansion fitting they should be able to produce a working solution. If they need a full dimensioned print to make one then they aren't an engineer and you need to look elsewhere.