Simple Google App Script (javascript) Fetch API request

We're looking of a developer to help us access the Amazon MWS API (Amazon Marketplace Web Service - [login to view URL]) using a Google App Script making a Fetch call, and save output into a variable. We want a functioning script to access the "Get Report" API request - returning the report in XLM or text format. (We'll provide an example ReportID + the SellerId, AWSAccessKeyId & Secret Key required my Amazon MWS). We've been having difficulty with making the Fetch request/Signatures etc. Apps Script – Google Apps Script [login to view URL] Amazon's scratchpad tool provides details on the request details, example below: ([login to view URL]) HTTP POST POST /?AWSAccessKeyId=XXXXXXXX &Action=GetReport &Merchant=XXXXXXX &SignatureVersion=2 &Timestamp=2017-09-07T17%3A38%3A38Z &Version=2009-01-01 &Signature=RMTPl9Xxv2JZzxRoZyOf%2FaTDpf4QQknk4toU%2FRZVe2g%3D &SignatureMethod=HmacSHA256 &ReportId=6357078170017416 HTTP/1.1 Host: [login to view URL] x-amazon-user-agent: AmazonJavascriptScratchpad/1.0 (Language=Javascript) Content-Type: text/xml String to sign POST [login to view URL] / AWSAccessKeyId=XXXXXX&Action=GetReport&Merchant=XXXXXXXD&ReportId=6357078170017416&SignatureMethod=HmacSHA256&SignatureVersion=2&Timestamp=2017-09-07T17%3A38%3A38Z&Version=2009-01-01