Its hard to go wrong with the Nuk5 for an adult, it pretty much fits most people well I believe. If you want to go smaller though, or just cheaper, you can find a few 16+ month styles on Amazon that aren't bad, they are the largest size you can get that are made for a kid,
https://www.amazon.com/gp/product/B00IOQ97JC/ref=oh_aui_detailpage_o05_s00?ie=UTF8&psc=1 . I 100% support buying silicon teats, as the latex tend to fall apart after a while. I'd only get latex if you really prefer it. If you want a really cheap Nuk5, the Aww so cute ones are actually pretty cute, but you will experience the problem with scratchy ridges, sometimes the stem isn't completely straight either,
https://www.amazon.com/ABDL-Pink-Ad...?ie=UTF8&qid=1499393397&sr=8-4&keywords=nuk+5 but it is a fun cheap pacifier. I don't have any background knowledge on any of the other pacifiers that you can find on amazon or of similar price ranges, but there are some pretty decent pacifiers out there for $20ish that are Nuk5. My last recommendation is pacifiersrus, they are good, but expensive. You pretty much buy from there when there is a pacifier guard that you just can't go without having, I have two simba pacifiers for instance, can't not have. I also got a Nuk7 because I was currious, and as cool as it kind of is, it is also a bit too long of a stem in my opinion. I get mildly annoyed with it after a while and switch over to one of my other paci's but I can still see some enjoyable aspects to having a longer pacifier guard, for one, it isn't anywhere near your teeth, its more like sucking on a lolly pop.
And sorry, I would post pictures, but at the moment I am lazy. If you look in my posts probably a year back you can find some of my paci pictures there.