So, If you don't want to expose your email address at all, I think you can just write down on your profile, like "I accept PayPal". Hope this helps.
I started to get spam (in reply to a Good Shopper forum posting) at an email address which I use for Paypal but which isn't otherwise visible on my ProZ profile page. A staff member explained that the only place it appeared was for the Paypal option. So now I simply indicate that I accept payment through PayPal without giving the address.