Pochade box recommendations for bigger size paintings

Hi, I have my Martlet pochade box and I´m very satisfied with it, BUT it´s only for small canvases only (aroud A4) and I´m looking for something for size around 50 cm/20 inches. Any recommendations? I don´t need wet panel carrier or so, just pochade box to mount on tripod. Thank you for your recommendations and happy painting to everyone!