Best replacements for KT99A tubes?

I have a pair of Cary monoblocks with two broken KT99A tubes. As they are impossible to find, my plan is to replace them with a full set of new-manufacture tubes. I was looking at 6550's, but not set on anything yet. From reading various forums, I've identified the Gold Lions, Tung Sul, and Svetlana, but I haven't read anything that makes or breaks the decision for me. I'm looking for any and all input or suggestions! This is all very new to me, and I want to get something that will do justice to these very nice amps.
Do you still have your old KT99A tubes?  I have a ST-120 amp with 4 of them, and unforunately one of them was broken, so I am looking for a replacement.  If you are willing to part with a couple, I would be very interested.  Thanks.
FWIW, I believe that there is little, if any, difference between the KT99 and the KT90. The former's designation as a KT99 was adopted by the tube manufacturer (relabeler?) and sold at a premium price. So I was told. I used the KT99 in some Sonic Frontiers mono's. Nice tube/sound. I replaced them with 6550's and KT88's over the years I had them. 
@_rossbower The guitar industry is really what drives pentode power tube production. It does not want anything other than KT88s because there are so many vintage Marshalls around and guitar players on the road want to be able to find a tube if one fails.

So there are some very good KT88s available now. JJ makes a blue glass (mentioned earlier) which is really quite good. I think you'll find in an amp designed for KT88s, that even though they make a bit less power, KT88s sound better.