Looking for a Steel Feather Spring

Hello, I need a steel feather spring that is large and sturdy. It needs to be wide enough to surround a decent-sized dildo and strong enough to offer resistance when thrusting through the head or backside.

So far, I haven’t come across any suitable options at hardware stores or online retailers. Right now, I’m checking out bike shops, though it’s still tricky to locate one.

Does anyone have suggestions, links, or tips?