Hi there. Which country are you in? The only 100 x100 cage I know of is a guinea pig cage which would need meshing due to the large bar spacing. Otherwise, it would be a diy cage. There are some large 120cm cages rather than 100cm square. And the large Eco Habitat is 115cm by 75cm which is big! But also very expensive.
https://www.littlepetwarehouse.co.uk...SABEgJxCvD_BwE
https://www.zooplus.co.uk/shop/small...r_cages/348156
This 120cm cage on Amazon Germany is good (they deliver to the Uk and Europe) - it is rather tall though so would need extra shelves to avoid fall risks.
https://www.amazon.de/M%C3%A4use-und...gateway&sr=8-1
A lot of people seem to be making the diy Linmon cage also - that is 100cm x 60cm. You might be able to adapt the idea to 100 x 100.
https://www.youtube.com/watch?v=Ocdcl-82ybE