Lensmate Online makes a filter adapter for the SX1/SX10. It bayonets on in place of the lens hood that ships with the camera. Canon doesn't make one presumably because the extreme zoom of those two would make designing a hood that didn't vignette at the wide end, didn't keep the lens from zooming all the way to the max. telephoto setting, and could hold a filter or an auxiliary lens would have been too much of a compromise. The Lensmate adapter is strictly for filters, not wide or tele adapter lenses. If you overburden it you may snap the bayonet mounting points on the lens barrel, or worse, break the lens drive mechanisms.
Some people have attached 52 mm filters directly to the front of their SX1/SX10 lens; it's not really threaded, so essentially they use the filters to cut threads into the plastic barrel. I emphatically do [i]not[/i] recommend this. Especially over time you're likely to shred the front of the lens barrel.