Is it possible to get the workflow token id for a catalog item request(ASD)? The only way i know of is other way around i.e. from workflow token to catalog item request. The workflow token has an attribute "attrRequest" which points to catalog item request.
Assuming you are using vRA 7.x, have you looked into using the Event Broker? There is a Pre Approval topic that I believe all requests need to go through that exposes a requestRef among other things. The Machine Provisioning topic also exposes a requestId, which you could try to force grabbing at the appropriate time by using Lifecycle State and Phase conditions.