I'm going to be the naysayer here for just a bit. Unless the two of you have made the leap to already playing around alternative, don't be too pushy.
Over the years, I've seen too many wives do things just for their husbands (seen too many wives dragged to threesomes, I guess) to make them happy.
And nipple clamps is just something a lot of men like to see but would be unwilling to do themselves.
As an example, and with a gentle nod to those who LOVE very raw and painful nipple attention, I don't like my nipples hurt. I hate those snakebite yellow things on myself. And at least once or twice a month there is a client who really wants to use some clover clamps on me or something similar.
Do they want those things on THIER nipples? Hell no. They want me to do it and possibly wouldn't care that I was doing it for them and not for me, because dammit, they hurt like hell!!!
So with exploring with things that HURT, don't push it. Please! If she digs it, then it's another story.
That's why knowing escorts who like that type of play is so great. And they're out there.
Sorry to sidetrack your topic. You've gotten a lot of good advice. But what I'm seeing is that you like the idea of a visual. If you apply some pressure with your lips and mouth, you should see a similar result with her nipples.
Otherwise, if she's interested, go for it. I've seen those suction cups used on a clit as well. I used to have a roomie that loved that! Makes me want to close my legs and not open them today just thinking about it.
Good luck,
Elisabeth