A strong neodymium magnet attached to your shoe or one of your components should be enough to trigger the sensor for the lights, I've seen them work on scooters and small motorcycles.
No worries! Some people suggest using a stainless metal case around the magnet since they tend to oxidize a bit, but there are a few good guides around with ideas.
Currently off my bike due to ill health but will suggest it to the cycling club.