Thin high carbon wire is extremley hard and springy, that is good i can tell you. The sort of wire you cannot cut with pliars.

Some of the bivvys use aluminium with angles on,you can buy them on ebay.

https://www.ebay.co.uk/itm/2Pcs-Aluminium-Alloy-Tent-Pole-Connector-Gear-for-8-5mm-Camping-Tent-Poles/362413907651?hash=item54618d5ec3:g:MqkAAOSwNmxb5yII