No helmet no ride – that’s an order!
Wear a turban. Sorted.
Wear a bandage, telling them you fell off your bike the day before, now your helmet simply won't fit. Sorted.
Wear a helmet & take it off 1m after the start. Sorted.
Get a doctors note for your itchy scalp. Sorted.
You get the idea...
Wear a WW1 helmet just to show them what fools they are.
A firemans helmet? A gladiator helmet? A childs play helmet? You get the idea...
Are they going to stop you? Of course not, at least not if you are not a mouse.
If they do, tell em to sling their hook and carry on regardless.