The helioplex(nothing special, just a mix of blocking agents) is good(and expensive) but, you need that good UVA/UVB combo. The best though is a physical barrier such a coated jersey coated in the new "UPF" treatment.

The most important thing is to use the stuff properly... don't simply go by the UPF rating, the sunscreen has probably been sweated off before you have to worry about running out of UPF. Reapply every 2hrs at least.

There are inorganic sunscreens such as the zinc ones.. but they are a bit tricker to work with, search the long-distance cycling forum there was some discussion there.