I don’t believe that I have seen an International theatrical for sale. (If this is the INT and not the US of course.)
I remember seeing an original theatrical 35mm print of The Empire Strikes Back from the UK a while back on eBay. And also, keep in mind that there are many different versions of Blade Runner. The International theatrical versions were different than the US theatrical release, simply because the International versions had a few more violent scenes than the US release (which were restored for the 2007 Final Cut release). This could possibly be a print of the European theatrical version that is being sold.