The Briefing office at Jacksons (POM) has ERC, VTC, Radio chart together with the PNG CAA DAPS. Reasonably priced I believe.
I am also told that a Rotary pilot/s from one of the companies at Jackson's of the Helicopter had put together a pretty good book of WAC/ONC type charts. That one did not sound so cheap but the product seemed pretty good.
Can't help with any contact numbers for either unfortunately. Maybe someone else can provide.