Hey Ben!
Hopefully I'm not too late to help. If you're looking for something fairly cheap, I've used this one from Amazon in the past and it's worked great for the price: https://www.amazon.co.uk/gp/product/B07B3ZKDR7/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
Although, back when I had a motorcycle, I did use a GoPro Session, which I picked up fairly cheap as it was used, and it worked great too, and the small size was a bonus. You can get them fairly cheap from CeX too, which is where I got mine from.
Hope this helped mate, and stay safe out there!