That's why it won't always be possible to find kanji for all words, or you'll have to invent a kanji for clock and another for watch.
Chinese, then Japanese, built their words on kanji, not the opposite like we are trying to do. But not all Japanese words have kanji, that's why they needed to invent the kanas. However words like television, telephone o photograph are easily rendred in kanji.

tele = far
vision = see/view
phone = listen
photo = light
graph = write

So, respectively 遠見,　遠聞　and 光書. If you start to invent kanji that aren't connected to the origin of the word (and therefore the pronounciation), you could just take the Chinese/Japanese ones. They are the most logical, but don't fit European words'etymology.