<p>Due to the lack of clientaccesspolicy.xml, there appears to be problems with using Amazon S3 via Flex. Are there any work arounds?</p>

<p><strong>Edit:</strong> Both of the below answers are great and work, I've upvoted both (I'm not going to assign an answer to the question as they both work):</p>

<p><a href="https://stackoverflow.com/questions/186768/can-you-use-amazon-s3-via-flex#186889">Can you use Amazon S3 via Flex?</a></p>

<p><a href="https://stackoverflow.com/questions/186768/can-you-use-amazon-s3-via-flex#194362">Can you use Amazon S3 via Flex?</a></p>

You can CNAME a subdomain you control at Amazon S3 (to a bucket with the name of the subdomain), like so:
http://s3.ceejayoz.com/
(goes to my 's3.ceejayoz.com' bucket)
Uploading your own clientaccesspolicy.xml file to the root of that bucket (and setting the permissions to be globally viewable) should do the trick, if I'm understanding your question correctly, as it will be accessible at
http://s3.ceejayoz.com/clientaccesspolicy.xml
.
More information in the S3 docs:
http://docs.amazonwebservices.com/AmazonS3/2006-03-01/index.html?VirtualHosting.html
edit:
From looking at that, you could also use the "Example Virtual Hosted Style Method" without a CNAME:
http://bucketname.s3.amazonaws.com/clientaccesspolicy.xml