I've never tried the Slavic paper, but I mourn the demise of any good paper. Just thought I'd share this formula: Manly Redevelopment Toner for blue black tones. I don't have any examples scanned at the moment. I've gotten very deep cool blacks with Forte Warmtone.

Bleach
Copper sulfate 50.0 g
Sulfuric acid 10% 65.0 ml
Sodium chloride 50.0 g
Water to make 1.0 liter

Developer Solution
Metol 10.0 g
Sodium sulfite (anhyd) 33.0 g
Sodium carbonate (anhyd) 33.0 g
Water to make 1.0 liter

Use the bleach and developer undiluted. I've never saved it, so I'm not sure about its shelf life. Wash well between bleach and redeveloping. And I would definitely contact the manufacturers regarding the Slavic paper.