the 135 lens will most likely work for 4x5 also, depending on the lens. 6x7 is generally handled by an 80-105mm range lens. If the bellows are so permeated by mold that wiping them down with a rag soaked with dilute chlorox and letting them sun for a couple days still won't get rid of it, worst case scenario you can make a new one in a couple of afternoons worth of cutting new ribs and gluing them to some light-tight cloth. There are patterns out there on the internet you can download to help you figure it out. If you're feeling a bit more flush with cash, you can probably contact one of those Chinese bellows-makers on Ebay and order what you need. Any other accessories you'd want for this enlarger would most likely be sourced on Ebay, with a lot of time spent hunting them down. You can make carriers for it out of black solid mat board, and lens boards can be made from 1/8" plywood. You'll need to make a baseboard, which you can do out of 1/2" plywood.