They just "feet\plates" in the ends of the stabilising legs.

I tries the plastic ones. Ok on parks and flat ground.
Don't last long on rough stuff.

I always weld up, 4 stainless, 4 sided flat "cups" up with two opposing tangs
each with a hole that a bolt fits through.

The stabiliser legs normally have a loop of steel as a foot on the ends.
The bolt fits through there
and the new feet. swivel to suit ground angles.

The cup section I fill with water or Talc. Keeps ants etc out of van from those points.
More talc round cable\hose, Tyres. drain, contacts with ground
will keep the ants (mostly) away at those points too.

Cheap Coles Talc does job. You'll appreciate it when you get up North.

I normally fold some plate up, then use 1in strap as the depth of sides and longer tangs.

Predrilled for bolts.

CC.
That van has gone.
This van still has a coupla moulded plastic feet on it.
and I've been involved with this Pain management\surgery trials etc for last 8 months.

I'll see if I can dig out a coupla old photo's and blow one up.

Though I don't normally take shots of vehicles. Usually it's places and old buildings
and the last 7 yrs or so have been all overseas..

Aluminium, or painted steel sheet will do.
I just have stacks of stainless from yachting days and steel yachts.

4 x lengths of 4\6 mm plate. around 4in wide and 6ish in long.
Fold the end up 1 inch each end.

coupla 4 in, lengths of 1 in x 4\6mm strap for other sides to form box.
Plus 2 x lengths of 6\8mm strap\sheet.
1 to 2in wide x 2 to 2 1\2 in long for tangs with holes to suit bolts dia

and weld them to inside faces of 2 of the sides.
Just check the 4 in measure. Some legs may have larger dia bases.

You want them just oversize, dimensionally,
so they'll free swing for uneven ground. but not bind in the leg itself.

God. It takes longer to write than to do hey.

Simple really though.
I also tacked a coupla pieces of 1\4 round bar under as grips\non skids too.

There are lots of little things you can do to a van to stiffen. Stabilise and make safer.
Quite cheaply. They ALL built to a price and ALL are lacking in some respects.

But those feet stabilisers combined with a trolley jack.
Are the best thing I've found for levelling and holding level. (IE NOt sinking much)
Any van

Ps.

if you have troubled folding any metal sheet etc.

An old trick.

Is to grind\Hacksaw. MOST of way through the material 

Fold it.

Then run a weld along inside of fold to stiffen. and strengthen it again.

B4 I made my Hyd folder. that's how I did most of mine.

Preheat if a bit brittle\thick.

Too easy.