Get a Sunpak 383. They are a great flash for manual off camera flash, and they cost only $80.00
See this nice review by Curtis:
https://photography-on-the.net/forum/showthread.php?t=242847
Also, see this nice other nice post by Curtis about using this type of flash off camera:
https://photography-on-the.net/forum/showthread.php?t=246797
You will also need:
- A hotshoe to PC adapter for your 430EX.
- A PC cord to go from your camera to the adapter above attached to the 430EX.
- A hotshoe to PC adapter for your camera (if your camera is a 300D, 350D, 400D or any other camera without a camera chassis sync connector). If you have a camera with a chassis based PC connection you will not need this (like a 10D, 20D, 30D etc).
- A PC based optical slave for the 383 flash (the optical slave will not work on a Canon 430EX).
Since you already have the lightstand and umbrellas, you should be able to get all this, including the 383 flash for less than the $150.00.
So, you will fire the 430EX with a cord connected to your camera, and the optical slave on the 383 will fire in unison via the attached optical slave.
Enjoy! Lon