Here are some pictures.

You wont find new, the drum company was purchased by Premier You may need a donor shell.

It looks like a spring can be used. That thing just looks like something to rattle inside.Never saw it before, can`t figure it`s use either.

I agree with odd ball that piece get rid. Replace with springs as that is what was in there originally. Springs easy enough to get hold of.

Can you show us that thing in the lug how it goes ?

Hello,

Here are pictures of this metal "shaft" inside a lug holding the two threaded nuts. These shafts are original, so there were no springs in the lugs at first.

These shafts grab around the nut, making a "click" noise when installed into the lug so they clamp and support the threaded nuts very well. Unfortunately this metal isn't very strong and bendable so the splittted ends break of easy. In the pic you can see oe of the ends has broken off.

Keep them with the drum because they are original. Without it, your top insert would drop into the casing.

I noticed the casing has no recess to slide the nut into to stop it from spinning. Just that spacer.

You may have to find a thin tube the same size, cut it to length, maybe grind it into shape with a thin wheel. Looks like Blued Steel.