Hi,
The pockets on the back of the seats was an option and can be retrofitted, i have the WIS work instructions and pt. no.'s of the bits you will require i was going to do this to my 43 but i got the price of the pockets from MB and decided not to do it, (in excess of £150 for each pocket!).
The ruffled pockets fit on the back of your existing seat backs.
I can let you have the details if you want them.