The filling mechanism of the pen is what tends to dictate whether there is a shutoff valve, and there two mechanisms that have this feature; vacuum fillers, and Japanese eyedroppers.

Vacuum fillers are generally higher end pens, but the best, cheapest option is a PenBBS 456, which is a Chinese pen. The Pilot 823 is very well loved pen in the community, and a good "next level" pen if you're looking for one. Viscontis are high end luxury pens that feature a vacuum filling mechanism, although their marketing calls it a power filler.

Japanese eyedroppers aren't really a "filling mechanism", per say, but can be thought of in that manner, even though you have to fill them with a syringe or pipette. Unfortunately far fewer pens make use of this, and tend to be very high end pens. The one exception are pens from Opus88, which pretty much all feature this mechanism, and are very reasonably priced. Then there's a big gap until you get to the high end urushi pens like the Pilot Emperor.

There's other one offs, like the bulkfilling mechanism from Conid and used on the PenBBS 355. The Diplomat Nexus uses an integrated shutoff valve that's engaged when capping the pen.