I got a second hand canon EOS 1000 and it does not have any lens caps and I was wondering where to buy some spares.
You should be able to get a lens cap from any local camera store, or easily buy one online.
For the majority of lenses, the only thing you need to know is the diameter in millimeters of the filter thread. This would be marked with an "ø", i.e. "ø52" would indicate a 52mm filter thread, and then you just need a 52mm lens cap. It doesn't need to be a Canon lens cap.
The only exception (as far as I know) is ultra wide angle and fisheye lenses with a protruding front element (the glass extends beyond the lens barrel) - but I find it unlikely that a 2nd hand EOS 1000 would be fitted with such a lens.