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A UK-based company called Hubs sells these geodesic dome kits.
They contain all of the hardware, but not the rods, for which you can use inexpensive materials; they recommend roof battens, hardwood dowels, broom handles or whatever you can get your hands on.
The design of the hardware is clever. Basically, you screw these ball connectors into the ends of whatever you’re using as rods.
The ball connectors then snap into the injection-molded hubs, and have a range of motion to them. This simplifies and speeds construction as you don’t have to have everything lined up dead-nuts.
Both five- and six-way hubs are included.
On Instagram and Facebook they’ve got fun galleries of user-provided projects. People have built everything from raised-bed greenhouses to chicken coops to music festival breakrooms.
Here’s a highly-satisfying time-lapse video that shows you just how quickly one of these goes up:
Core77