Decent arms are quite robust on these cars. OE (TRW) are best but any quality brand would do. Ocap, Moog, Firstline (Borg & Beck) would probably be ok. You may need mounting bolts. If they break, be aware the are M10 with 1.25mm thread pitch. There are 3 different lengths of bolt per arm. They are very high tensile (marked 10.9 and not the usual 8.8). They are better than normal zinc plated bolts.
Look on EB Spares or Alfa Workshop for information.