I have been considering using a twist grip from a motorcycle as a replacement not because mine broke but because its terrible.
that said this link
should have what you are looking for.
as per the kill switch, if you clip the peg out from inside it (or drill a second hole in your handlebars) you should be able to back it up against the new grip and continue to use it.
but if you are replacing the throttle anyway you could opt for purchasing a higher quality kill switch or getting a replacement throttle that has one attached.
finally about lube: I have used a few drops of my chain lube for this purpose, but some people on these forums have been adamant about using a dry lube on your cables (graphite powder) makes a lot of sense to me, but whatever type of lube you use just make sure to lube them tubes regularly. also keep an eye out for your cable bunching or folding because that can really mess up your day.