Hi Andrew
I've got German MR Footrests rearsets on my Evo so, when a friend of mine said he was thinking of getting a Monster 1200S but didn't like the stock footrests either, I found these for him. (He's not got the bike yet so I can't give you any first-hand feedback on the footrests themselves but the ones I have are really well designed and beautifully machined.)
I'm not 100% sure they would fit the bike you're looking at as the website says they are up to (and including?) 2016. Best to check with MR themselves.
https://www.mr-motorradtechnik.com/e.../%22D%20240%22
They come with a separate exhaust hanger, which is quite neat.
Note that you have to send them your original footrest mounting plates in exchange.
Based on my experience with the Evo, I'll say that, if I were going to buy a 1200S, these are the footrests that I'd fit.