@drewfer A Pilot 912 with falcon nib with a custom regrind down to needlepoint and with extra flex added (Called a Mottishaw Spencerian Modification).

There are a handful of modifications you can get done across many different pens. About 4 or 5 different models I know of off hand accept this particular modification. You usually pay about 100 euros for the modification on top of the price of the pen itself. You can get this from nibs.com

If you want a cheaper option that can get a similar quality script, but is just more likely to railroad, so you get your money's worth, you can make a frankenpen. Basically buy an ultraflex nib and a ebonite feed from fountain pen revolution and insert it into a different pen body. My personal favorite is the 5.5 nib and ebonite feed which fits perfectly into a TWSBI Diamond body. I love clear demonstrators.