Your search for "(corrugated) cardboard" revealed the following:

Paper corrugated board [pitch approx. 0.7 mm] 200 x 19 mm, 5 sheets: Northeastern Material HO(1:87) 40100

Loading cardboard (small) : YSK unpainted kit N (1:150) Part No. 469

Cardboard box (loose) : YSK Unpainted kit N (1:150) Part No. 471

Tin corrugated sheet "row" : Baioudou HO (1:83) unpainted kit AC-044-83U

Loading cardboard (large) : YSK Unpainted kit N (1:150) Part No. 470

Tin corrugated sheet "Magyokusa Set" : Baioudou N(1:150) unpainted kit AC-046-15U

Tin corrugated sheet "Kusa" : Baioudou HO (1:83) unpainted kit AC-045-83U

Tin corrugated sheet "row" : Baioudou N (1:150) unpainted kit AC-044-15U

Corrugated tin sheet "Kusa" : Baioudou N (1:150) unpainted kit AC-045-15U

Tin corrugated sheet "Magyokusa Set" : Baioudou HO(1:83) unpainted kit AC-046-83U

Corrugated board 2.4 x 1.6 x 76 x 279 mm, 2 pieces : Northeastern Wood, non-scale 6021

Corrugated board 3.2 x 1.6 x 76 x 279 mm, 2 pieces : Northeastern Wood, non-scale 6022

Corrugated sheet 1.6 x 1.6 x 76 x 279 mm, 2 pieces : Northeastern Wood, non-scale 6020

Corrugated board (deck plate) 2.0 x 1.0 x 150 x 300 mm : Evergreen plastic material, non-scale 4528

Corrugated sheet 1.6 x 1.0 x 88 x 609 mm, 2 pieces : Northeastern wood, non-scale 70426

Corrugated board (deck plate) 1.5 x 1.0 x 150 x 300 mm : Evergreen plastic material, non-scale 4527

Corrugated corrugated siding, 2 ply: PLASTRACT PLASTIC 1:24 PS-26

Corrugated corrugated siding, 2 ply: PLASTRACT PLASTIC 1:16 PS-27

Corrugated sheet 2.4 x 1.2 x 88 x 609 mm, 2 pieces : Northeastern wood, non-scale 70436

Tin corrugated sheet "Shin" : Baioudou HO (1:83) unpainted kit AC-043-83U