You can access a single content unit at: /pulp/api/v2/content/units/<type id>/<unit id>/ but that does not seem to be documented in our REST API. It should probably be documented here: http://pulp-dev-guide.readthedocs.org/en/latest/integration/rest-api/content/retrieval.html
https://github.com/pulp/pulp/pull/702
Confirmed. Moving bug to VERIFIED.
This has been fixed in Pulp 2.4.0-1.