As previously suggested, every Part 121 1900 in the U.S. has a flight attendant - he/she sits right next to the PIC. You can tell any pilot who's flown the 1900 for any lenght time because that person can brief any emergency exit in less than 2.1 seconds.
I have actually heard a rumor that an airline in Australia operates their 1900's with a dedicated flight attendant and even a lav, which is an option on corporate 1900's from Raytheon.