I am working on an old SKS and have not been having much luck with the birchwood casey's super blue. I have heard great things about Brownell's Oxpho-Blue as far as cold blues go.

It is sold out as brownells and unavailable elsewhere as far as I can tell. Online auction sites (not sure if I can mention by name) do not show any current listings either.

Is this something that regularly comes in and out of stock? Or is this the result of the pandemic creating shortages in supply? Any suggestions on where to get some or another well liked product?

Thanks in advance for the help, guys.

Not mine but here is what appears to be a pretty good evaluation of several products:
Evaluation of several cold bluing products (w/pics)

Here is the winner so to speak from that post:
Nu Blu

Personally haven't tried it yet but was about to order some for and upcoming project. So if you do and its crap let me know

Oxpho Blue is awesome.  Got some just a few months ago.