Explorer 39mm curved spring bars (and rubber straps)

SHE is buying me a new 21470 Explorer as long as I promise never to marry her and also to find her a s/h Cartier Tank down the line so we can wear watches instead of wedding rings (Some might call this a win/win/win/win).

Any idea where I can find curved spring bars that will fit safely please? I'm in the UK.

Want to try a Nato and also rubber straps.
Nato I've been reading that the straight Rolex spring bars are too close and I need curved spring bars (?).
Rubber straps I've been reading threads on Everest - again any pointers there would be greatly appreciated.

(Pity I can't invite you to the reception.)

Thanks!