Small Tunnel Shapes

I'm in the market for some new anti-insect mesh to protect my alliums from the leaf miner and brassicas from flea beetle and as my hoops made from left over rebar aren't really big enough I though I'd invest in some supports too. But why is everything round, meaning that the outside edges can't be easily used?
Does anybody make/sell rectangular frames to support mesh or plastic? I can't find anything on the French market, beyond modular solid plastic cloches.
I may have to set MrPP a task, although he still hasn't made the bench from the tree my neighbour cut down three years ago ...

I have some square ones made from bits of pipe that slot together to make a "box". Bought them years ago but I've seen square ones made from plumbing pipes/conduit.

Only thing I can think of is getting a fruit cage but cover with the insect mesh.

I'm thinking about plumbing pipes with bubblewrap sleeves over the corners - the rebar just wears out whatever is over it and it would be much worse with corners.

Foam pipe lagging is good over joints to stop wear.

This stuff https://www.screwfix.com/c/heating-plumb.../cat831554

Oh yes of course! I have a length of foam pipe lagging on the side of my bedside table for when I bang my head on it in the night!!

Gardening naturally do walk in square domed frames, also square cloche frames - but they're out of stock!
 https://www.gardening-naturally.com/alum...quare-hoop