Might be a hard find.... but you never know! I would look in our classifieds here at the forum first. Post a "wanted" item if you haven't done so yet. Next I would contact all the vintage trailer types, they often have left over parts from older trailers they will sell. I know I was looking for a 63 knob awhile back and took a picture of what I wanted and emailed it to a number of vendors. Most replied with a yes or no! Look on ebay as well! I would check craigslist in your area too. I would also contact all the folks who have the same model/year as you here at the forum via personal message and ask if they know of anyone who has an extra. Never know you might find someone updating theirs...
Mrs. NorCal Bambi (traveling in S Tardis)