Are you replacing them because of the crack I see in the picture? Those are castings, and most aluminum castings are very easy to weld repair. I've welded tons of aluminum castings over the years with good success, but don't own a welder right now. If you took them all to a good welding shop at one time you might get them repaired fairly cheaply. Also you could get them vibratory polished and reanodized, they'd look like new.
My Etap 26 has completely aluminum stanchions, no stainless. However they used a large stainless bolt to mount them and many are badly corroded due to electrolysis, way beyond welding repair. However mine are machined round pieces, and I do own a lathe and mill, so I will be making new ones.