Single cab Rear sliding window seals?

[buttrock slp ss]

I have a 79 c30 dually single cab that has a factory sliding rear window it sat for 12 years before i plucked it out of a gravel lot, my question is. Does any one make seals for the sliding window? the window seal around the whole window is good. Just the sliding part felt and rubber is bad? I noticed the rubber seals are pretty much rotted away so if it rains alot it will trickle in the cab. Any input is appreciated