If you are interested in purchasing Cambodian stamps, please send me your 'wants' list and I will send you a list of prices of those available here in Phnom Penh, Cambodia, including prices for those items available at the Philatelic Counter at the Central Post Office in Phnom Penh:
Other internet sites that I have found to be selling postal history - including stamps - of Cambodia include the following:
SOLER Y LLACH SUBASTAS INTERNACIONALES, S.A. in Barcelona, Spain: STOCK SALES >> Postal History >> Other Countries: http://www.soleryllach.com/soler4/stock/l/23?filtroVD=0&nivel=2,3