That is what is called a pipe davit. Davits can be made by any aluminum or stainless steel tubing fabrication shop, so there might be hundreds of suppliers.
One large supplier of these is Nick Jackson, see Pipe Davits
. But his current ones at least have a small truss that strengthens the davit but your pics don't have that. Also your pics show reducing sections as you near the end.
Why do you need to know? To get a rough idea of the lift rating, compare the diameter of your outer pipe with the diameter of Jackson's davit without the truss. The physics of the loads on that outer section should be approximately the same so they need to be the same diameter for similar weight capacity.
For example, Jackson's pipe looks to be 2-7/8" OD for 300 or 500 lb davits. Compare that with yours.
If you want to buy a winch, then Nick Jackson probably could help, no matter who built it.