Yes, the KSN 1038, 1041 and 1056 are all the same except for cosmetic differences.There are no suitable drop-in replacements. However, you may still be able to purchase KSN 1038's from Universal Electronics at (800) 533-3350. Ask for Bob Heintz.
CTS is looking for buyers for the piezoelectric tweeter business line. My guess is that they will probably be successful in this, because it is a well-established business with lots of ready and willing buyers. But who knows what is in store during the transition period and, if they are sold to another manufacturer, it remains to be seen if they maintain the same quality control and what not.
Personally, I'd like to see another manufacturer pick it up, so the tweeter line goes back in production. The one complaint I had with CTS was that they pretty much just threw the tweeters in a bin where the finish could be scratched before you ever received them. It would have been nice for them to add fifty cents and individually surround them in a protective package or put them in an egg crate type of device for shipping.
As for the current situation, I've got a bunch of KSN 1038's in stock and I'm looking for other options before they run out. If CTS sells to a reputable manufacturer before I run out of inventory, I'll keep using them if the price remains competitive. If not, I'll choose another part. Lots of good ones out there, but for the power handling and response of the piezo's, the price will have to jump.