For a non-slipjoint gentleman's knife, the Nemesis Imp (available from True North Knives) is an excellent choice that doesn't get mentioned too often. Another possibility is to check out the locking knives section on A.G. Russell's website. He has a pretty decent selection, the website is one of the best around, and they are great folks to deal with. If you want to go with a custom, there are several good internet dealers.