RE: camera arm
None of the good ones do - considering the 501's heads we use cost $180.00 alone - you won't find a "cheap" replacement. Big, heavy fluid heads produce the best footage. The same reason most guys use a stabilizer to tame the "shake" in a bow.
If you intend on getting serious about filming, you better have some money to blow. It never stops and nothing is cheap. It's not a cheap sport man!