I wouldn't imagine the box being available on it's own after all this time, it's nearly 30 years old now. I was lucky to find a guy selling a completely sealed box on Amazon back in 2016 and it's still sealed and sitting on my shelf. May well have been a canny buy as it looks like cassettes are are making a kind of resurgance in the collecting world. Don't know if I paid too much for it but at £73 I thought it was a snip and just glad to get them. Good luck finding the box.
Cat# entered is for box set, Cat# for this tape should be BLN12. Also delete images 1960062 & 1960063, wrong ones added. Correct images added and need shuffled. Correction submitted