Here is the budget way to get an arm rest in your 450 fortwo or Roadster.
Go to Smartmods and buy the bracket. Obvious step 1 really. In the kit, you will get:
2x 25mm Allen Head Bolts,
1x 20mm Allen Head Bolt,
3x Nyloc Nuts,
Tools for fitting, you will need:
6mm Allen Key,
8mm Drill Bit,
Smaller Drill Bit.
It's laser cut and hydraulically bent by a company in the UK.
It's oiled to stop rusting so clean it up and paint it the colour you want.
Place it against the side of the seat and mark the position of the holes.
Depending on how tall you are, you may want to set this lower than shown (I'm 6'2").
With the hole centres marked...
...drill them out with smaller drill. 5mm is perfect.
Then re-drill the holes with an 8mm drill bit. Clean the metal swarf away (a magnet works well).
Place the 2 longer bolts through the washers, through the arm rest bracket and into the seat.
Pull the foam to one side to access the thread of the bolts. Be careful of sharp metal swarf behind here.
Fit a washer and a nut over each...
...and tighten them up.
Take your selected arm rest (selecting the ideal arm rest is covered later on).
Pull the cap out of the side of the arm rest and drop the remaining shorter bolt into the hole (thread first).
Slide it onto the bracket making sure that the locking tab goes into the rear of the 2 holes.
Add the washer and the nut...
...and tighten it up.
On most of these arm rests, there is an adjuster wheel underneath.
Wind this either way to set the correct arm rest height.
The arm rest can now be folded out of the way when not required.
This bracket was designed to be able to fit on either side (but not both at the same time. More on that later).
At the time of writing, the correct arm rests are really quite cheap. However this may change with popularity.
There are 2 different styles of locking tabs. The right version has 1 tab and will fit straight away...
...but the left version has 2 locking tabs.
The lower of the 2 tabs needs to be removed. Just hacksaw it off.
It takes about 1 minute and now it'll fit the bracket.
Some of the cheaper arm rest designs don't have an adjustment wheel as they are set at the factory.
However, this isn't a problem as they can still be adjusted. Look in the end and pop out the cover.
You'll need an unnecessarily long flat blade screwdriver to adjust it.
With this one opened up, you can see the adjuster at the base.
You just have to twist it 1 way or the other to set the correct angle before putting the cap back on.
Firstly, you need to decide if you are having it on the right or left hand seat and get the appropriate side.
Fire up eBay or get down to a local car breaker and start looking for the following.
VW Transporter T4
DOUBLE CHECK the photos of the arm rest to ensure it has the correct mounting plate.
If you know of any other vehicles, let me know. There are Audi symbols on some of them.
You can only fit 1 of these to a car. There isn't enough room for 2.
You cannot fit an arm rest to each side of 1 seat. The door won't close.
The arm rest can only be fitted to the side nearest the hand brake.
If you buy the arm rest for the wrong side, it will stick into the boot.