I know of www.ladegueter-bauer.de.
Very nice and well executed.
AFAIK they are Märklin's main supplier for most of their special editions.
Saw them at the Nürnberg Speilwaremesse in early 2013, and can only say positive things about the products and the people.
Cheers

Hi Dan,

I make my own inserts for coal, ballast etc. I cut a piece of expanded polystyrene to fit the wagon, then I shape the polystyrene by picking at it with my finger nails, and then I paint it black. For a more realistic effect you can then sprinkle finely ground coal over the whole thing, holding it in place with PVA glue, but I don't generally do this as I feel that the polystyrene painted in matt black looks about right.

For other types of loose loads you can cover the block with sand, model ballast, cat litter, or just about anything.

Loads like wood can be well represented by cutting matchsticks and glueing them together in stacks, and pipes can be made from drinking straws.

There are a lot of very interesting loads made by Hornby in their Skaledale range, and these are not expensive. I have loads of wooden beams, cable drums, cars covered with tarpaulins, crates, logs etc, which look realistic and easy to swap between wagons or just leave in goods yards.

The most important thing is to have loads of fun (sorry)!

Thanks Ray. Are must admit, I was being a bit lazy seeing as I do a lot of scratch building already! I have spent a lot of time building new houses and station area out of kits and from scratch. I have it in mind to do coal loads for bogie Eaos opens and then stone loads for type fals SNCF opens. Trains of stone are moved from Caffiers in Northern France, so there only list as my layout is modelled on the area.