Kind of amazed when I saw that Cabelas had these 10 and 20 round drums in stock:
http://www.cabelas.com/product/ProMag-Saiga-Shotgun-Drum-Magazines/1318792.uts?Ntk=AllProducts&searchPath=%2Fcatalog%2Fsearch.cmd%3Fform_state%3DsearchForm%26N%3D0%26fsch%3Dtrue%26Ntk%3DAllProducts%26Ntt%3Dsaiga%26x%3D0%26y%3D0%26WTz_l%3DHeader%253BSearch-All%2BProducts&Ntt=saiga&WTz_l=Header%3BSearch-All+Products#BVQAWidgetID