Near rhymes:
* cautious
* fractious
* precious
* vicious
Eye rhymes (words that look like they rhyme but don't sound alike):
* atious (this is the suffix that makes "nautious")
You could also use words that have a similar sound but aren't exact rhymes, such as:
* nervous
* anxious
* uneasy
Ultimately, the best rhyming word will depend on the context of your poem or writing.