I went back to P7 on the FH a few months ago - still a great rubber. So I then went through the same thought process about finding a replacement once stocks dried up. The suggestions here are all pretty good TBH, but it depends on how close to P7 you want to get. NL's suggestion of 5Q+ is good, and I'd like to throw Donic Baracuda in there too.
P7 is an old-gen tensor now. If you like how they played then it's probably best to try and stay in that general area. I actually sent an email to ESN asking if anyone there knew which rubber was the closest to P7 in terms of construction (after all, they make all the tensors so they should know). I didn't get a direct reply, but I did get a spooky PM on a German TT forum a few days after asking if I was the person who sent the email. After a short back-and-forth, they said that Xiom Omega IV Asia was the closest in terms of nuts-and-bolts. Now, I remember O4A being a bit faster than P7, but I recall the topsheet being very similar, so this makes some sense to me.
However! I find that I play better with the plastic ball with the newer-gen tensors overall - I feel the older-gen topsheets slip sometimes, especially in humid conditions. So if you wanted to try a more recent rubber with a hard sponge/soft topsheet combination like P7 then Xiom Omega V Asia is the closest I've tried (which is just sheer coincidence WRT the above suggestion from the mysterious German), but again is faster than P7.
