Congratulations on your "new" 69! The forums here are very helpful about roof vents. Another great source of info can be found at
www.vintageairstream.com. That website has a section about Restoration Rescources and a subsection about repairing Roof Vents and Covers. I was able to find a replacement Astrodome for my 64 Tradewind at
www.airstreamdreams.com but, according to what I've read, I THINK InlandRV might have one that fits the 69 a bit better. And, don't forget EBAY! I've become ADDICTED to that site for those random extra parts that I can't locate elsewhere! Good luck and welcome to the Forums!