This is the mini USB version I bought for my previous camera on Amazon but for the Viofo I use it with a mini to micro USB adaptor.
https://www.amazon.co.uk/dp/B074M4XM...p_mob_ap_share
They sell a micro version as well, just search for Rearmaster OBD on Amazon. It is either always on as long as the battery is more than 11.6v or switches off with the engine after a few seconds. Details are in the listing.