(more band-y but still cool)
Similar to the Entwine/Interlock are these from beyondtherockz at Etsy, both $70 in sterling silver, but I've asked and you can upgrade to 18k gold for around $400 depending on the metal market at the time.
(I figure this one as a 'for her')
(and thus, 'for him')
I like the symbolism, not as much necessarily the knot or being tied but how there's no end to the pieces, it's a continuous loop.