B&H has Fomapan 400 in 120 for $3.89/roll. You can also get Fuji Acros 100 from them for the same price if you buy it in a 5-pack.

If you were looking for 35mm, you could get Kentmere 100 in a 24 or 36 exposure roll for $2.95 from them. Kentmere films are made by Ilford.