I used to have a 1995 Simplicity Broadmoor. I realize it's smaller machine than your Landlord. I had a 36" single stage blower that was actually branded as a Honda product. It turns out the identical blower was used by both Honda and Simplicity. The only difference was in the hitch kit. I did have the Simplicity brand hitch.
So if you are looking at used items, you may not have to restrict yourself to only Simplicity branded attachments. Perhaps with a bit of research you can determine exactly what the Simplicity branded attachments are, then do the same research for say Honda or Cub Cadet. You would want to look carefully at the way the blower mounts to the hitch. I suspect many of these blowers attach to the hitch exactly the same. Only the mounting of the hitch to the tractor is unique to each make and model. At that point you may be able to buy a used attachment and only have to order a new hitch from a Simplicity dealer.
Just a thought.