No sweat here Jimbo, that's what their posted for.
That's just a tubular metal film capacitor, with a lead coming
out of each end. It sounds like the caps you're looking at
are polarized radial electrolytic types, which is not what
you want.
Antique Electronic Supply out of Tempe, AZ is one who stocks
the metal film type. You won't find a .57uf cap, it's not a
standard rating. A .47uf or .68uf will work just fine, it's
not real critical, neither is the polarity on this type of
capacitor. It may just change the tone a tiny bit. It's
just a function of the charge/discharge time, that is, the
larger cap takes longer to charge up which will lower the
tone the smaller will raise the tone. Also the new caps
will be about 10 times smaller than the old one, better
technology now days.
https://www.tubesandmore.com/products/C-T-630V dg