Terry has a knicker that is designed for indoor usage, so it *might* be lightweight. There is another thread where a woman found a sun protective running tight that she found useful, but you still needed riding shorts under it. There was also a thread about Islamic sports wear, but those are probably designed for heat, not necessarily sun.

We've got solutions for long-sleeved jerseys (Boure and the Canari that TE sells), but we're still falling short for tights. Loose fitting pants are probably your best bet.