I bought a copy on Ebay a year or two ago. There are 3 copies on Ebay (search for "warp 4 OS/2") at the moment (plus a 4th that is missing the CD).
There may be pirated copies out there, but I don't think you want to go that route.
There's also [link|http://www.ecomstation.biz/cgi-bin/db2www/biz_art2.d2w/report?catname=eComStation11|eComStation] that is supported by the vendor (unlike Warp 4 unless you buy a contract from IBM).
HTH.
Cheers,
Scott.