Welcome to Miniriders,
Yeah it sure is a KV75.
They were made between 1971 and 1980, you should have a frame number stamped into the fork/headset tube that will help you work out what year your bike is.
I reckon there'd be a lot of corrosion inside the Housing/Switch and contacts, it might be repairable still?
Take the throttle off the handlebars, there will be a couple of philips head screws holding the switch into the throttle housing, undo them and the switch should come out, or apart.
Clean up the brass switch contacts with some steel wool and CRC/WD40 then wipe off any corrosion/dirt etc,
give them another light spray and reassemble the switch back into the housing,
You should be good to go.
If something is worn out, or broken, if you can't buy a new replacement, you might be able to replace that part with one off a similar year Kawasaki.
Handlebar/Switches etc 1971-1975
parts kawasaki kv75 motorcycle accessories spares replacement aftermarket
Handlebars/Switches etc 1976-1980
if it isn't repairable, then disconnect the kill switch wire down near the coil, and tape it up secure.
Then buy a new aftermarket one that bolts to the bars and use that instead
You can get them cheap off ebay etc, might need to fit new crimp on terminals to suit the KV wiring loom
Kill Stop Switch Horn Button 22mm Handlebar Switch Motorcycle Motorbike 7 8" | eBay
Universal Handlebar Kill Brake ON OFF Motorcycle Switch Button Bullet Connector | eBay
http://www.ebay.com.au/itm/ON-OFF-B...28?pt=LH_DefaultDomain_15&hash=item4188b9aed0
http://www.ebay.com.au/itm/Ner-Mini...rcycles_Parts_Accessories&hash=item3aa1a940c0