I had the same problem, I was told there was a version 2 coming at some point where the issuer would be added. Until then there is a graphql hack where you do something like
$qry = 'query { markets(baseAssetCode: "XLM", counterAssetCode: "GOLD", counterAssetIssuer: "GBC5ZGK6MQU3XG5Y72SXPA7P5R5NHYT2475SNEJB2U3EQ6J56QLVGOLD") { tradePair close }}';
contact me directly and I will give you some working code.