I mean, I work on custom software that my clients use in-house; my clients always get full source code and I bill them for my time. But I doubt that's particularly relevant to your situation.

I don't know what would work for you. If you're doing in-person support for your users, that may well be a lot more valuable than the software itself. Maybe that's a viable business, or maybe it isn't. Again, the world doesn't owe you a business model. If you're selling shrink-wrapped software then my honest opinion is that that business is dying (with or without the open-source movement) and it's better to get out of it.