I bought this sparge arm a few years ago:
Stainless Sparger large : Northern Brewer
It works great, except for the small PVC caps on each end of the arm. They fall off when you crank up the pressure, and I don't like PVC in my system at all.
In any case, Wayne at Bargainfittings turned me on to these replacements and I thought I'd pass along the tip. MCmaster part number 92805K17. $2.26 for a pack of 5 silicone caps. Should work perfectly.