light pollution filters for canon

where can you purchase light pollution filters to fit a canon lens ( 58mm diameter)?

Also, are nebula filters worth while for a canon ( with 300mm lens) if the camera is unmodded ( i.e, the IR filter is not removed)?

I think you'd be better off getting the Canon modified by Baader first and later trying the filter route.
If you add filters then you'll need longer exposures - is you're tracking up to that yet? Are you using a guide scope? You will probably have to once your exposures start running up over a minute or two.

No, My tracking isnt up to that at all just yet.
I was hoping I could use standard techniques but just use more exposures in the final image.

I currently have a canon, and I cant afford another one and dont want to modify my current one, which is why i started to look in teh direction of filters.