What area of math are you in?
(After googling): Number theory. So obviously NSA is an option. They hire grad students for the summer, encourage your students to do this if it interests them. Also encourage students with programming chops to spend a summer doing an internship at a big firm that owns their own low-level compute stack, which will necessarily include crypto components. Intel, Apple, Microsoft, GPU manufacturers, ARM, Broadcom, etc. It may be hard to get your first few students in, but once you place a few and get introduced to their bosses you'll have contacts and it'll be easier.
Cast a net outside your field, too. Some students are studying number theory because it's interesting, but aren't wedded to doing it forever. It's worth talking with them about what they're really looking for and nudging them to take some CS / stats / finance courses if they have wider interests.
Finally, as a former math grad student who left to go to industry 10 years ago, thanks for even thinking about this. Most professors don't, and you're already doing your students good.
I'll send you an email with some more suggestions.