I am not sure the exactly place to buy the pearls in Doha, but you could consider to buy the gemstone beads online, which will be very easier for you. Here I would like to recommend you a wonderful pearl supplier, who is the leading pearl wholesaler and they only supply high quality freshwater pearls and seawater pearls: http://www.stunninggemstones.com/cn/products/Wholesale-Pearl-Beads.asp