3 brothers emigration from Risen/Stadsbygd area

Have exhausted everything I know to do to find ship's records of 3 brothers, with no luck. I would appreciate it if someone could please point me in the right direction? Emigration dates are from US Census, Minnesota. Peder Odin Johnson, Born 1871, Emigrated 1889 (All may also have used "Pederson" instead of "Johnson") Benhard S Johnson, Born 1869, Emigrated 1891 (Also spelled "Bernhard/Bernard") Martin Ole Johnson, Born 1877, Emigrated 1893 Family in 1865 Census, Father Peder Johnson, Mother Olina Pedersdatter. (Distriknr 6, Side 113, Skoledistrikt Ritsen, Sogn Risen, Prestegjeld Stadsbygd, Gardsnavn Nostbraettingen, Overskrift 1. Post 721-727) Any guidance would be greatly appreciated!