The site-recommendation tag here on Meta Stack Exchange exists for exactly this reason. According to the tag wiki excerpt:
After looking through the site list, https://stackexchange.com/sites, don't know where to ask your question on the Stack Exchange Network? Give as much detail as possible about the question you'd like to ask, and the community will help you find the appropriate site. Please phrase your question explicitly as a site recommendation, or it might be closed as blatantly off-topic.
So, basically, if you can't find the right site, ask for a site recommendation. Make sure that it's clear you're asking where to ask X, not actually asking X. MSE gets a lot of blatantly off-topic questions every day, and your question may be closed if it's not clear that it's a site rec.
This question you asked is actually a good example of a site recommendation. It's clear that it's a site recommendation, it has the site-recommendation tag, it's got a good example of what you want to ask, and it's got a fair amount of detail.