Al,
If you're having one built, you can order what you want, and I wouldn't recommend adding the DST unless you really want to build a Germanic gun. If you're buying, you won't find a lot of US or Brit guns with set triggers. Although I know of one McKay Brown bolt action in 270 with a single set trigger. He told me ha made it for a rabid stag stalker (the stalker, not the stags) Go figger. Otherwise, some companies like Steyr Mannlicher and Sauer made fine high-grade production rifles with set triggers. The German and Austrian custom makers quite often put them on their guns. As MP notes, they are pretty much the rule on single shots. So, you may well find one if you look over there. Have fun,
Leo