try using profiles and AMi search functionality

cookiecutter.json

@@ -1,6 +1,5 @@
 {
   "full_name": "Chris Mague",
-  "email": "github@mague.com",
   "packer_name": "packertest",
   "short_description": "description goes here",
   "release_date": "2018-01-05",
@@ -8,8 +7,6 @@
   "ruby_version": "2.4.1",
   "terraform_version": "0.11.1",
   "min_ansible_version": "2.4",
-  "allow_duplicates": "no",
-  "galaxy_tags": "",
   "dependencies": "https://github.com/shokunin/ansible_ec2_base,yatesr.timezone,bennojoy.ntp",
   "target_os": "ubuntu",
   "aws_region": "us-west-1",

{{cookiecutter.packer_name}}/packer.json

@@ -1,8 +1,5 @@
 {
   "variables": {
-    {% raw -%}
-    "source_ami"     : "{{ env `SOURCE_AMI` }}",
-    {% endraw -%}
     "region"         : "{{ cookiecutter.aws_region }}",
     {% raw -%}
  },
@@ -27,13 +24,19 @@
     {% raw -%}
       "profile"     : "{{ cookiecutter.aws_profile }}",
     {% endraw -%}
-      "access_key"    : "{{user `aws_access_key`}}",
-      "secret_key"    : "{{user `aws_secret_key`}}",
       "region"        : "{{user `region`}}",
-      "source_ami"    : "{{user `source_ami`}}",
       "ssh_username"  : "ubuntu",
       "instance_type" : "m3.medium",
     {% endraw -%}
+      "source_ami_filter": {
+        "filters": {
+          "virtualization-type": "hvm",
+          "name": "ubuntu/images/*ubuntu-xenial-16.04-amd64-server-*",
+          "root-device-type": "ebs"
+        },
+        "owners": ["099720109477"],
+        "most_recent": true
+      },
       "ami_name"      : "{{cookiecutter.packer_name}}-{% raw -%}{{timestamp}}{% endraw -%}",
       "tags"          : {
 		  "role"       : "{{cookiecutter.packer_name}}",