Hi Ian - yeah the tubular item on the rear LHS fender is as you suspect, a later style night driving distance/convoy spacing light, and apparently had a deep blue lens held by two circular end brackets which were just in vehicle colour (ie. dark yellow) with a thin curved metal lens guard/blackout cover that spun around it. It was used from perhaps mid-late '44 seemingly only on the tracked vehicles. It replaced the earlier style boxy-looking one previously seen on all motorised equipment as part of the NOTEK firm's night light system which had the 4 small green lights on the upper half and the hinged flap with the red and orange stop light and blinker crescents below which remained on most other vehicles throughout the war. FWIW here's one of those early types on a Kubelwagen belonging to a private collector in Sydney I took a few years back with the flap shown up and down. The bottom section was covered for night driving with the 4 green lenses showing and only a pin hole in the flap showing the red of the brake light when applied, while the flap was flipped up for normal daytime driving to show the brake and blinker lenses more clearly;
These were quite clever in that they allowed a driver to gauge his distance from the vehicle in front by how many of the 4 lights he could visually make out. 4 distinct lights meant he was too close, 1 solid bar of light meant he was too far back and 2 separate blocks of light he was at the right distance;
As the later ones you're interested in were only a fairly fragile glass tube like a flouro its sadly now very rare to see any still intact on museum vehicles these days - usually just 2 bent circular support ends are all thats left.
The 2 circular items on the fenders themselves are indeed as you guessed just simple reflectors and are a deep red - Tamiya or Gunze clear red are perfect for replicating it. The shot below shows one of Panzer Museum Munster's Jg.Pz.IVs I snapped last year which while missing the distance light at least has the 2 fender reflectors though post war repros which are more than a touch bright;
Hope thats of some help.