Cameta Digital Slave Flash (50$-60$) : (Not Avaliable)
Have seem some good reviews about Cameta Digital Slave Flash and its seems good for its price which is around 50$-60$. Fully compatible with Canon PowerShot Digital Cameras and nearly all other Digital Cameras with tripod-socket including: Casio, Epson, Fuji Finepix, HP, Kodak Easyshare, Minolta DiMAGE, Nikon Coolpix, Olympus Stylus, Panasonic, Pentax Optio, Ricoh and Sony Cybershot Digital Cameras.
Pro Digital Auto Slave Flash (20$-30$):
Pro Digital Auto Slave Flash comes with Bracket Set for Canon PowerShot A480, E1, SX110, A2100, A2000, A1100, A1000, SX200, SX10, SX1, SD780, SD880, SD990, SD970, SD960, SD1200, G10, D10 Cameras. Another good slave flash for your SX10 to use with. You can read more details as Amazon. I saw this Flash for around 20$ at Amazon.
Phoenix D92-BZS Digital Slave Flash (60$-70$):
Phoenix D92-BZS Digital Slave Flash is another slave flash I saw while looking for cheap external flash for Canon SX10 IS camera. I don't know much about this flash but its within to range you can call cheap. Phoenix D92-BZS Digital Auto Flash Product Description says it bounces, zooms and swivels. Also says it has a hot shoe so that it can be fired from the camera too. Check the link for more details