Looks like the Heliopan price list shows the 82mm 10 stop filter, which in price group 2 comes to 132 euros, including 16% tax. That's what my rusty German gets me (accuracy not guaranteed). See the 5th line on page 7 of their price list .pdf.
Just did some checking, and Heliopan is now distributed by HP Marketing. Bob Salomon at HP has been very responsive to email contact for me and others. Perhaps the best way would be to contact him directly about availability at:
bob@hpmarketingcorp.com
Hope this helps.
Lee
Just noted that I'm repeating David, but the email address is new.
I use a 10 stop B&W ND filter to test reciprocity failure for astrophoto films.