I think the B1 is difficult to come by; the company’s web site shows they’re no longer available.
You might look into getting a used Yamaha YDP2006 digital parametric EQ. They sell for about $100 on eBay these days. In addition to equalizing, it’ll do a 24 dB/octave HP down to 20 Hz, and also do a 24 dB/octave LP. So it could be your equalizer, crossover and subsonic filter, all in one package.
Regards,
Wayne A. Pflughaupt