I don't understand, if it's .6mm smaller isn't that the size, too? They have sleek top caps (in different finishes) on their site for purchase, but, not switches.
I just went to their site, and I think MMV's naming convention for their new 22mm seamless Nanos Sleek might be causing some confusion. I see what Portertown is saying and see the confusion that you're having... if i had a seamless, I'd be confused... I think MMV needs to clarify what's what on their site a bit better now.
Traditionally speaking, their "classic" top caps belonged to their poldiac classic and had the indentations on them... then they released their Poldiac Sleek which removed the indentations. And I believe those same topcaps are interchangeable with their normal Nanos line (along with all their Poldiac tops caps for that matter).
Now with the new 22mm seamless Nanos Sleeks, the naming convention is a bit confusing... The term "sleek" which most associate with the non-indented poldiacs is also being used in connection with their Nanos... Problem being that the Nanos line never had any indentations on their topcaps to begin with.
So the two types of top caps i see on their site are: 1) Full Top end cap for Nanos (various finishes); and 2) Top end cap for the Poldiac/Nanos Sleek (various finishes).
If I had to venture a guess, neither one of these caps are for the 22mm seamless Nanos.
Option 1 seems to be the full top cap for the 22.6mm Nanos... with contacts and all. Option 2 appears to be the top cap only (no contacts or insulator) for the Poldiac Sleek and Nanos... Since its for the Poldiac, which is 22.6mm, it would NOT be for your 22mm seamless. And really, the only difference between these two options is the inclusion of the contacts... primarily because the Poldiacs don't need the contacts while the Nanos would.
I presume that MMV will have (or at least SHOULD have) a completely different section for their 22mm seamless parts on their website as all of their prior offerings have been 22.6mm.
Bottom line: Don't get confused by thinking "Sleek" parts refers to your 22mm Nanos... as it has traditionally been used to describe the non-indented caps (as Portertown pointed out). The 22mm is sort of a different beast from the traditional MMV stuff and you should probably keep an eye out for the "22mm" designation for your spare parts.
Notwithstanding... the 22.6mm caps and switch will still work on your 22mm... just not be absolutely flush. (i've previously asked MiriamWTH). But to be absolutely sure when ordering, you should probably verify everything with MMV directly. Obviously since they could change the info on their site, etc. at any given moment.