How many teeth? Pressure angle?
Stock Drive Products carries some internal gears. Go to their on-line store and search on "internal."
Rush Gears will custom make them for you, but you will pay through the nose for them.
Are you sure you need them in steel? Boston Gear makes 24DP and 32DP internal gears, 1/4" face width, in brass, with both 14-1/2 and 20 degree pressure angles.
Arrow Gear makes a large assortment of internal gears, up to 17" pitch diameter.
You can also find several more gear manufacturers at
powertransmission.com.
-dave