I love DIY stuff and have done a similar egg crate box in the past. Not as polished, but focused on functional.
However I found the following which was about $25:
https://premiumaquatics.com/products/choice-aquatics-md02-acclimation-box-dual-medium.html
Notice the pictures show a single square box, but look at the measurements and the description of 'dual'. I ordered and the box is great. It is twice as long and is a one-piece continuous rectangular box and not the square on the picture if you leave out the optional divider. The closing lid allows me to target feed as well. I double checked my invoice and it was for the model: YCA-CMD02. Great little find!.