Anne Summers do lil round plaster things to cover up nipples when wearing see-through things... perhaps those will work. I can imagine when they get sweaty though... yuck. I've never had a problem with chafing of anything though so... I have nothing more to add on the subject other than...
hahahaha, guy with bleeding nipples *giggles*
This is nothing compared to the guy I'm actually talking about (although this dude was also in the sheffield half).