Are there alternatives to an NHT X1?


We inherited a set of NHT speakers.  We have one A1 amp, but no X-1 crossover.  I cannot find an X-1 for sale online.  Based on the diagrams, we need an X1 and another A-1 to power the subwoofers properly.  Is there a workaround?  FYI - we are novices so please forgive any basic questions:)
eak22270
You have 2 passive NHT subwoofers , 1 mono amp and no X1 external crossover? 
Only thing I can think of is trying an active crossover like a Minidsp 2x4hd, of course you'll need another amp to use both subwoofers. 
This may be your lucky day!  I have a A1 & X1 I have not used for years.  Message me here.  If we can come to an agreement I'll post them for sale here.