An aftermarket lower rod should work. Years back, I picked up 2 or 3 lowers from Anderson Detector Shafts for my Tesoro Bandido II Umax and my assorted coils. All of the upper shafts should be the same on these units, the only issue may be... if Anderson still manufactures them. IIRC, there was a little difference in length on the aftermarket versus the stock lower rod. I believe that the Anderson was slightly longer, but with the adjustment pins it was a non-issue anyway.
They fit and work just fine, and came with hardware also. Used 'em for years, and no complaints on my end. They are light, and were inexpensive at the time.
Hope this helps,
HH
T