Many companies that's been around for 20 years have bazillion pieces of unexciting software they need to support and maintain. They still need full time employees to keep them running.
Want an example? Adobe Sign. Here is a product that they can never stop supporting. The software doesn't need more features, but they still need security updates and maintenance.
Just pick a big, old technology company and browse the job listings. Look for "old school tech", like Java EE. Just add it on your resume and say you worked with it a long time ago. Boom, an interview.
edit: Scripting languages like PHP or Ruby will also have lots of legacy software around them. But Java software being "enterprise-y", tend to die off less frequently, and people there seem treated better than legacy PHP programmers.
edit2: In a large company, there will be boring, maintenance areas, and exciting areas. Try to interview with boring teams, since that is your goal.
Disclaimer: I'm not affiliated with Adobe in any way. It's just an example I know outside of my own work. We have examples too, but that would be too revealing.