One of the popular agile books put it this way, when you write new code, it stays new for about 10 minutes. After that, any changes are code maintenance.
I'm not sure what you are looking for, but unless you find a) a startup who is still working on version 1.0 of their product or b) a software house that does custom software for individual customers and move on, you will find that most companies are in what you call "maintenance/enhancement mode".
I joined my company when we were on version 2 of our product and currently we are about to release version 7. But there was plenty of new development work which under your classification would be considered "an enhancement" that you want to avoid.
I think what you actually want to focus on is not whether or not maintenance/enhancements happen but whether or not the company has long-term goals for a product. There are certain products that once they reach maturity level, all new development stops and there's no more major releases. In these cases, an engineer might get hired strictly to fix existing bugs, deal with tech support and possibly provide minor enhancements here and there. In this case, I would agree with you that this is the type of work I'd like to avoid.
So you could take a look at their products, ask which ones you would be working on and then ask (better lead engineers than managers) on what the long-term, maybe 1-3 years, vision is for the product. If they stumble and not give you a vision, then it's a full time support position, but if the engineer gets excited and starts talking about all the cool "enhancements" that they want to add, I'd guess there would plenty of new development for you.