You're referring to what was originally the C4i-30 from your description, the 1930 riveted Eilzugwagen (E30 for short) in 3rd class, which after the 1956 class reform and the renewal programs as B4ywe-30/50

Which EraII version are you after?
Era IIb before 1938 in brown-green with the eagle in the top middle
Era IIc from 1938 in bottle-green with the imperial eagle in the middle? (nazi symbol but manufacturers omit that detail). Also suitable for EraIIIa after removing the eagle.

The Marklin mould is originally from 1979 and has the bogies too close to the middle. Fleischmann also did the B4ywe-30/50 in a much better design.
Liliput also did an E30 but I don't think there is a contemporary EraII version.

You can see a comprehensive (but no means complete) list of E30 models here:

https://www.modellbau-wi...80.9EHolzklasse.E2.80.9C

I don't believe Marklin released theirs in an Era II version, possibly because that would require model changes such as scissor grilles instead of bellows and roof running boards.
Fleischmann have two nice models but neither have the roof running boards which are expected for EraII versions:

Fleischmann 567706
Fleischmann 567703 (end of train boards)

They don't come up very often though.



Because of this, I will mention there is also the C4i-36 which is the welded version and overall very similar with the double doors at each end.

You can see a comprehensive (but no means complete) list of E36 models here:

https://www.modellbau-wi...80.9EHolzklasse.E2.80.9C

More recently Brawa and ESU did the E36 wagons in a contemporary design but there is also the Roco version which is good and still being sold in new versions today.



Pullman (ESU) 36144 and 36145 recommended for Era IIc
Brawa 46151 and 46152 for Era IIb

If you're after a budget wagon, then the older Roco 44551 can be picked up very cheap for Era IIb and is a good model.

Marklin do Era 2 models of course but speaking as someone who only models Epoche IIIa you will always need to diversify your brands if you want a complete lineup of wagon types for your chosen period.
Era IIb like IIb is a common period for modelling and tends to have more models available, more so than IIc or IIIa.

Era IIa for Germany is 1920–1924 which is before the riveted eilzugwagens were built, so we must look at only era IIb for these wagons then.

This means the Fleischmann models for the C4i-30 and either the Roco or Brawa for C4i-36.

I have several of the Roco 44551 which I converted to Epoche IIIa and I can recommend them.

https://www.modellbau-wiki.de/wiki/Epoche