hi newt on swings
i have a few different portfolios.
the least expensive one is made by pratt.
it zips closed and has a binder type ring system
so you can get replacement pages when the ones in it
get kind of grungy. it is the rolls royce of mass produced portfolios.
i also have a few hand made ones made by portfoliobox (.com)
leather bound hand made to your specifications. if you want, they
can make a slip cover / box for it. i have 2 11x14 ones, one landscape one portrait,
and 2 8x10s the same way ( L+P ) ... if you want one that is handmade portfoliobox is the way to go
they are great folks to work with, and have been around making custom boxes, and cases, and books
for probably 25-30 years. i live in RI and have been lucky enough to meet them ... and can't say enough good things about them ..
good luck !