Forum Discussion
Do you have the often discarded bundle of manuals that come with all new RV's? If so you might be able to find out who made the original tank and see if they are still in business. Alternatively you might try joining the glamisdunes.com forum and post there for ideas. They are going to have a lot more RV's with fuel stations than you'll see here.
Are you looking for someone to just rehang the old tank or somebody to source a new tank and hang it? To just rehang the old tank I would google up a mobile RV repair guy or two and see if they'll take the job. They might even take on the task of sourcing a new tank and installing it.
If you want to try to source the kit yourself I would search for "toy hauler fuel station kit" I did that search and on the first hits after the Amazon links I found