First piece of advice, never toss anything without knowing the availability of a replacement. Never toss a hood that isn't too crumbly to use. I've cleaned up very ugly hoods using lacquer thinner, but it sounds like you don't have that option now. Shimano used a different hood design for most models of levers, so you will have to look for hoods specifically for that model of lever - or be sure of cross compatibility. They may be out there for your levers but without checking for the specific model I don't know. The easy solution may be a new pair of modern Tektro levers. Likely to be less expensive than a NOS pair of hoods to fit your original levers.