With regard to L-rods and pendulums, you may make you own if you are so inclined.
Any heavy weight
( as simple as a "tear drop" fishing weight/sinker for example ) attached to a length of supple
string / thread will suffice. L-rods need to freely rotate. One means of doing so is to find a length of copper wire
( stiff enough to hold the L-shape ) and a copper/brass tube that is slightly larger inside diameter than
the outside diameter of the wire. The wire will easily rotate inside this tube. Hobby shops/hardware stores have
such things.
Or you can buy these, which is easier
