Happy Birthday vhdos! I love how you chose such a classic Cartier watch to commemorate your 40th, it is a significant piece to honor this.
In agreement with the others, if you want to stay in the luxury range, maybe a Love bangle, the rose gold color looks very nice on you. Was going to suggest a diamond bezel set tennis bracelet. That would be gorgeous.
There have been a few threads recently on stacking watches/bracelets, plus the popular Pandora thread, with many gold bracelet creations. My budget dictates more silver in my jewelry and I am addicted to Pandora bracelets -- you can mix and match charms of your choice. It's great stacking piece for my boyfriend watch.