I found a great simple button that mostly met my needs - except for one thing. It fit into the hole but didn't stay there when removing the PTFE so every time that I released the PTFE tube there was a good chance I'd lose the button down the back of the cabinet. I looked for others and found a couple with clipping action. One was way too far involved an install. The other was a poor design that meant the clips were super weak and you really needed to be extremely careful with it.

Enter this one. Each ‘clip' is half of the button so no chance it'll break at the layer lines. It inserts easily and clips well but if you do ever want to remove it you can still do so easily enough without having to take the hub off the printer. Now all my hubs have one of these in place and I'll never need to revisit them.