A 4x4 pressure treated post is inexpensive to buy but extremely expensive to ship. If you need the "Y" post but don't have the tools to build one please talk to a local handyman/friend/neighbour/etc.  
This one will require a drill to put together but the parts will be cut and predrilled, screws and construction adhesive will be included.  Will be wrapped in cardboard and shrink wrap. May get dented in shipping.
5' long plus angle pieces, brown pressure treated 4x4 post.