The shelving April got is from Ranchhouse cages on ebay. I've had some of theirs. They come in all different sizes along with the cage bar attachments and fixings. I particularly like their coloured bendy bridge that attaches to the bars as well as the shelves - I have two of those
https://www.ebay.co.uk/sch/m.html?_o...Shelf&_sacat=0
This one comes in different widths and depths and you choose the size you want
https://www.ebay.co.uk/itm/30cm-Deep-Solid-Pine-Shelf-Platform-Rabbit-Guinea-Pig-Chinchilla-Cage/290403118250?hash=item439d5fecaa:m:mbgA_Wl7BBYkKIm uxp9tjwQ:rk:23f:0