You need an over the aperture solar filter, its been a few years but if i remember correctly this is mylar that blocks out 99.999% of uv and blue light, you can buy this by the square foot for i think around $20, never use those solar filters that thread into the eyepeices, the intense heat can crack the filter and cause serious eye damage
or blindness.
a full aperture filter is not required, you could make it 5" diameter and hot glue it to a cardboard ring that fits over the tube with the filter off-axis, its also important not to scratch the filter material, and make sure there is no pin holes. or check out thousand oaks and pay alot for a glass filter.