Not all instructors and educational resources are on .edu domains. And many of those non .edu resources have comprehensive links pages that they're happy to give you a link from.
Searching on things like widget instructors, widget courses, and anything you can think of related to education in your niche is likely to provide a rich list of potential link sources.
Book publishers and authors are a good example of this type of educational but not on a .edu link. Niche book publishers tend to have authoritative websites and be friendly to others in the industry. And many of them have comprehensive links pages.
Yes, 'sponsorship' type links are reasonably easy to get from .edu's. Anywhere they'll republish a link for some reason other than asking for a link, not on a student or prof subpage. Some educational institutions republish their newspapers as well so if you can get a link in their paper (easier than you imagine if you think about it) you get an archived link on their site, or if you contribute to your alma matter sometimes that's good for a mention.
*Note: I've not done any of these myself. These are pushing the paid link envelope pretty hard. They may still be good links but you'll have to evaluate the risk.
a case of beer may qualify as a roofied link; which if administered to an underage personal .edu holder can raise a handcuff penalty.
the alma mater idea sounds doable. although i haven't been as active; i should, as my school is like 2 blocks from here; i joined their web design group, but they barely congregate. thnx for the idea; for i'll start to see where the journos go.