Raphnet (and possibly others) make a USB adapter for Dreamcast pads, if you have one.

If you want something brand new, Xbox controllers have a more or less direct lineage from Sega pads, as (iirc) MS hired many ex-Dreamcast personnel to work on the original Xbox after the DC was killed off.

360 pads work well on PC and are easy to come by. Hyperkin also makes a modern version of the original Xbox ‘duke’ controller that might work well.