AVOCET SYSTEMS INC., 120 Union St, P.O.Box 490
Rockport, ME 04856 do a wide range of assemblers
and cross-assemblers. The address is elderly but
you should be able to track them down. Another one
worth calling might be AD2500 Software (address unknown,
sorry, but try a large software house for a lead on the
address). AVOCET products are very nice, but rather
expensive, at least here in Australia. Hope this helps.