Re: Where? Jacks for welded-bracket-style trailers?
The replacement ones that I get, have the welded part included. You have to take a snap ring off to seperate the two parts. Then you have a piece like the one shown in SBN's post.
I do not know if all companies have the same hole size, so you might need to order a replacement from the same company as the original.
I have also seen ones that do not come apart and you have to grind the old one off and weld in a new complete unit.