(Don’t miss out!) Get them while they
last! (?)

Классно, по-моему!👍

Замечательно. That's it!

when it's gone, it's gone

How about "Don't miss out! Grab it while it lasts" ?

That’s also very good!

Thanks, как говорится, a load!

Oops!
I forgot my initial question about "А ТО И..."
It can be interpreted as "otherwise EVEN..." Something like in
A: "I'm not sure it's what I really need"
B: "Don't hesitate! Otherwise, even this one will be out of stock soon, and nothing's going to be left at all."
In Russian, the phrase sounds humurous because it implies the situation in the Soviet Union, when everything was hard to get - the era of total deficit.

the era of total deficit.

It looks like a Runglish. А как правильно, интересно

era/times of shortages of(/in) everything

Instead of EVEN, we’d say TOO: Don’t wait, otherwise they’ll run out of this too and then there won’t be anything left.

👍🙏

Just scoop it before it’s all gone!

👎🏼