Where's a good place to order supplies online? It depends on the supplies. Harbor Freight, Amazon, Camping World. If you do a search on the forum for the specific supply you are looking for, you may find a good source.
... motorized dolly... Short dolly discussion
...mice / varmints... A good tomcat that can live outside. If you search for "mice" on this forum, you will find a few posts with comments and solutions. Better to do the search, as there are various options to choose from.
Good luck! We love our TM, as most here do.