I'd just go with the vivarium you linked then!It's definitely a good upgrade,even if it won't be quite a full square meter(still much better than a Detolf or your current cage!).
Tanks do get expensive,and they're difficult to move.I can't blame you at all for not wanting one,they're definitely not for everyone and they have many different drawbacks that make them fairly impractical anyways!
As for other ideas there aren't many things I can think of.If you wanted to mesh a guinea pig cage there is a 100 cm x 100 cm one,but the dimensions make it at least somewhat impractical for some people.That would possibly cost more than the vivarium though,and you'd be limited with substrate depth.There's the double Detolf(impractical and very expensive compared to this vivarium,but an excellent 2,000 square inches while doubling the depth!),or there would also be a Lack but instead of using two units for the cage you'd use four and you'd end up with a slightly over a square meter cage.That in mind,the vivarium would be easiest to modify and it would probably be a few square inches short of a square meter at most anyways
