In the absence of a local group/community that you're looking for, how about creating your own?
Every group starts with someone having an idea and putting it out there.
As founder, you would also have a lot of latitude on what your group encompasses*, and what activities** it does.
* Options include autism/asperger's only, to include anyone neurodiverse, and also whether you intend to focus on autistic adults, or include family members and allies as well.
** I've seen groups that do online meetings only, those who do in-person (whether at a cafe/restaurant, at a community centre or library where you might get free space rental, recreational activities, etc.), and some that have a combination thereof
The main thing is to make sure that you don't promise too much to start with as you might spend the first several weeks or months building up membership before starting any events as you don't want to risk having events that are really small, as that can be intimidating for some - speaking for myself, I'm not comfortable having extended one-on-one conversations with people I don't really know).
Meetup is a pretty good platform in general for running meetup groups, though social media may work as well, with the caveat that some people don't participate in social media and so you're excluding a segment of your potential membership. Speaking for myself again, there are some groups that are of interest to me but which I haven't joined as they exist solely as a Facebook group and I don't use Facebook.
Good luck and if you'd like support or to share thoughts/ideas, please let us know and I'm sure someone could share some thoughts and ideas!