The 09 Internationals have hollow core doors on the bathroom - they may even have had a window in the door - tho those were discontinued in many models somewhere in the past. The bedroom never had a door, it was a sliding fabric thingy. Only the classics have sliding doors to the bedroom. If you choose to get this trailer negotiate the price seriously because you're gonna pay too much for replacements.
You should be able to get replacements from any Airstream dealer close to you - but they won't be cheap.
I'd suggest that you put a "wanted" ad in this site's classifieds as a lot of people remove the bathroom doors to get some knee room.
I've seen one or two units where the owner put in heavy quilted fabric curtains on a traverse rod over the bathroom door. IMHO "privacy" in a trailer may be sight related but you can still hear every sound. I think a good lined curtain could give you better sound isolation - and you could leave it open an inch or two at night so the bath wouldn't get so cold overnight.
Today is a gift, that's why they call it the present.