22 tooth rings are still pretty much standard for MTB triples so weenie replacements are plentiful.
20's - There are a few around but Carbon-Ti make a nice 20 tooth chainring for 64mm bcd cranks. It's probably one of the easier one's to find too IMO.
Making the chain run smoothly isn't a huge deal for most cranks, the pic below shows that a little work with a file is needed for clearance and that's about it.
The S-Works crank could be bought direct from the website at one stage, US$300 for the arms but unfortunately I think you have to get them from a dealer now. Last I heard, the pricing was the same or similar. The spider and chain ring spacers can be bought from Lightning, the spline pattern matches the S-works cranks.
If you want to look at Hollowgrams at all, IMO your best bet is to spend some time on eBay or similar sites and look for some bargains. Being Modular, it doesn't matter if you find road/MTB versions, you can swap spiders and spindles to suit your needs.
The Hollowgrams are likely to cost more than the S-Works because they have such a cult following. The S-Works can also be found on eBay at great prices, often barely used or even the occasional new bike take off.