I didn't find the photo of La-5 with armored windscreen - all are without (i.e.
photo). But all La-5FNs (I guess) an availiable photos have it.... Drawings in "Samoliety Lavotchina" by N. Iakubovitch show armored windscreens on La-5F.
You're right about Yak-1b - a lot of tham had "broniesklo" in front of the cockpit - but this plane was in production till half of 1944 (from"Pierviy Yak" by Kuznietzov)