Go for 5x4 internegs made with an enlarger. When they were available as sheet films, both Ilford XP2 and Kodak T400CN made great black & white interneg films. Ilford Delta100 would be my choice now but you'll need to experiment with development regime to get smooth highlight rendition. Any 35mm s/s interneg was always a compromise in terms of quality, so the duping attachments are of limited value.