Wotname is looking for an analogue mechanical engine water temp gauge that displays a temp band from 40C to 80C.
That is 120F to 175F for us North American metric illiterates
I don't think he will find one,but here is a link:
Water Temperature Gauge 52mm with audible Alarm - AMBER BACKLIT - www.roadrunneroffroad.com.au
I suggest an exhaust temp alarm
also. I use one by Borel Mfg. The sensor clamps around the rubber exhaust hose & has an included wire & loud beeper.
Just provide +12V from "Ign" or whatever.
Next : Google
Digital water temp gauges Australia
. Got several hits including ebayAU for <$30--again racing gear
The same in Marine
will be several xx as much per usual.
There are also "self powered" cyl head temp gauges for small engines-bikes,atv's,snowmobiles,etc that have a sensor that goes under a headbolt,or whatever, & no ext. pwr reqd.
A water temp sensor (Mech. or Electric)must go into the water in the water passage
or hose. It will not be meaningful if you just tee it,like you can with a oil
pressure gauge. This means finding an extra tapped hole into water jacket,or replace existing electric
sensor with a mech. one. Mech. sensors typically have a longer sense element than electric senders.This means you need enough depth
in the water jacket to accommodate it,without it hitting the "back of the hole" & touching the interior
Most sensors are standard NPT national pipe TAPER & I believe BNPT/BSPT? British TAPER thread is compatible.Stay away from NP Straight or British equiv.-they are meant for seacocks & other special situations & do not seal by simple tightening.
Hope this helps