They’re far and few between. Just watch ebay or any other reputable seller and just keep your eyes open. I look for the 74’s I have (really good and right below the 75’s In quality) all the time and I rarely see them up for sale/bid.Where does one find those 1975 Reflektor tubes?
I’d like someone’s take on both years who own both. Looks like everyone just hangs on to them. Maybe someone on this site wants to sell them? You never know.
Post in the classifieds WTB in the cables, Speakers , accessories thread for this particular tube and see if anyone bites.
Good luck in your search.