I've looked around blades for those ordinary stationary band saws and for the band saw I checked out that takes blades of length 59 1/2" (I won't say the exact product, as I don't want to sound as if I'm promoting it), it's specified that the blade width can go from 1/4" to 3/8".
Looking at other blades of length 59 1/2" from different brands, I've seen one that is even 1/8" in width. Though I don't know if the the stationary band saw mentioned can handle it.
I've ordered a portable band saw (again, I won't say the exact product) that takes blades of length 44-7/8". The manual of the portable band saw I ordered specifies 1/2" width of blade, with variation only TPI, but no other choice for thickness or width.
I've looked at other brands of length 44-7/8". At this point, it seems that blades of length 44-7/8" are meant for a number of portable band saws from different brands. I've checked these 44-7/8" blades from different brands and it seems that it only width it comes in is 1/2".
So is that the rule of thumb that portable band saws blades only come in fixed widths, as they are only meant for cutting straight through?