There is a haban sickle bar mower for bolens large frames such as a 1250 on ebay. The seller lists it as being for a tubeframe but from the numbers given, model 415a series G it's a large frame attachment. Looks very clean, even has a perfect "sickle-mo" decal!
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=50377&item=4321563615&rd=1&ssPageName=WDVW
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=50377&item=4321563615&rd=1&ssPageName=WDVW