Not many will write stand alone sled insurance. Economical has a restricted list , however if the broker presents a strong case they will write a sled on the list. If your record is clean and you have auto home etc. with them they can write your sled if the broker bothered to push them on it, I have several sleds insured for clients with Eco that are on the list .Each has a good record and are mature ( age wise lol )
I would question the Eco broker and see if he asked for a concession for the sled.