Best Pearch is still wood. Soft wood. It important for finches. I got mine at B&Q
Here is the hack. Cut and sander to mimic a tree branch sand it down to your disire length and diameter
Saw a grove between to fid at wire cage to stablize it at both end or spend money on twist on perch end. But if you got breeding box wall then all wire cage use this few hack idea rather then spend more money.
They are like coke can pin ( drill a screw hole on flat top and bend out a little. Perch goes through the hole. Tension of perch against wall and other against cage front would made perch wobbly.
The others like the cap of twist toothpaste, tomato tube paste or any cap diameter large enough for perch to fid in the hole. Screw cap to wall and fix perch to it.