The DWSM774 Dogbone V to Eyebolt Ratcheting Clamp connects any 3/8" rod (straight, L-arm, Z-arm, or whatever) to a cymbal stand down-tube. Using this small piece of hardware, you can attach any instrument with a 3/8" mount underneath one of your cymbals without taking up much room.
This clamp is 7" long overall and both ends are angle-adjustable so you can get your instruments in just the right position.