I know that this was only your "fall-back" but, just in case you're not aware, the chassis for these is the standard chassis on all of the "ToyTrain" series wagons (94xxx) from LGB, so you might find it economic to buy second-hand ToyTrain flat or gondola wagons (those with bodies moulded in 'vivid' colours go for less).
You don't tell us what you're planning to do with the chassis but, If you are after a platform at each end (as per the feldbahn), you should look for the caboose (94065 etc.) which has a variant in the chassis moulding (there is a slot to take the railing just behind the buffer beam at both ends), though these occasionally turn up on underneath other ToyTrain wagons too!
EDIT: Having checked my facts, it seems that the ToyTrain chassis with slots (to take railings) at both ends are more common than I imagined - maybe even universal in recent times. Maybe the ones I've "chopped about" were very early examples, or maybe my memory is playing tricks. If you need an extra railing, PM me. I've got spares removed from ToyTrain wagons when I 'anglicised' them. i can't help with the extra "flooring" section, though.