I was an old skool raver in early 90s England - we got our whistles, lanyards etc from exactly the same places referees got them (traditional sports and outdoor goods shops) as well as things like fishing hats which were popular back then.
From memory there wasn't much rainbow imagery on the rave scene, simply because LGBT+ folk were always a major part of the UK dance music scene from the mid 80s onwards and did not really drift apart until the mid-late 1990s..