If the whole thing it is just for two pipes maybe the solution PTvor work for you cheaply! Not sure about the quality and strenght of the actual weld .
It is very trick and I think to take a really good answer you have to give more details about the size of the pipe etc, so other members more expert may contribute and give you some feedback.
Well I purchase a pack of 100 Esab 316 Rod 3.2mm for £16 from Ebay.
Make you maths!
aidank stainless steel has grades according with the grade you will have to use the right electrode.Myself do mainly 316 and 304 stainless steel stuff so I always have some 316L and 304 one.Even most of my stainless steel stuff done with Tig and filler rod as I found it more tidy