One thing you can do is check your local autism organizations to see if they know of anywhere you can find respite care. You may also be able to find respite care in your local yellow pages or on Google. For using Google enter - "respite care" "your city, state" - and this should bring up something if anything is available.
If you're financially able, you can look on Sitter City or Care.com. Both of these websites have listings for caregivers that have experience caring for people of all ages on the Spectrum. You'll have to check your area. There is a fee to be able to contact the care providers. (Check in our footer for any discounts.)
If you're unable to physically get away just yet, find some time for yourself at home for now. Make it a point to put this on the schedule as a priority. For example, taking a hot bubble bath while reading 4 more pages from the book you started last year, after everyone's asleep, can be a nice little vacation at home. You could wake up an hour early and snuggle up with a cup of coffee or cocoa and listen to a podcast or read the paper.
If you aren't able to fit this in before everyone wakes up, you could even do this in the middle of the day with your child. Yoga is great for kids on the Spectrum since it helps one to calm and focus.
For information on respite care, here are some helpful articles:
A helpful book for relieving stress: