It really depends on what you can find. You won't have any more luck finding new 7800 or 6600 shifters than you would 7700 9 speed. Probably you can find new 6700 or 5700. In theory the 7900, 6700 and 5700 with concealed cables are not optimal for your older brakes. I have found, in practice, that they work just fine. If someone has tried them and they've not worked, maybe they will chime in and you will have a YMMV situation. I'll also mention that you can still get new 9 speed DA bar end shifters, that's my solution for the bikes I want to keep 9 speed.