I think the Raf derbies have the nicest shape in the market. I agree retail is high, but they can be had on sale if you are patient. Viberg make a good pair of derbies as well, but priced around Dries' so maybe too high.
With some of these suggestions like Alden, Heschung etc, we are getting into off duty office bro territory, an area Occulta wanted to veer away from.
For my own edification, what constitutes 'off duty office bro'?
It also kinda depends on cut and color of the denim; black or grey may be easier than indigo, especially washed-out indigo.
IMO Buttero makes decent shoes in pretty casual shapes, and they're not terribly diffic ult to find on sale. Fiorentini + Baker shoes have a really casual shape as well, although they're maybe not as nice as Buttero and don't get a lot of love around here. Randomyooxbrand binary code-by-Italian name sometimes has some plain-toe stuff as well: http://www.yoox.com/us/men/shoponline/01000010%20by%20boccaccini_d
Are you specifically looking for long, thin, & slouchy? I got one from Cruvoir house brand Parlay a couple of years ago for a pittance that's may have some aesthetic similarities, though I'm not sure they make them any more. If you want something thicker and warmer, Wolf vs Goat popcorn knit beanies are insanely cheap and really nice (whole-fashioned construction or something like that, so no seams), and they can be worn slouchy. The downside is that it's a preorder from basically a one-man operation and delivery times can be unpredictable. Also they launched a couple of weeks ago so they may have sold through most of their stock, but you can always shoot Mauro an email (wvg at wolfvsgoat dot com) to see what he has.