You should be able to use Spring Expression Language to get the behavior you want, without using another bean. The following works for me in Tomcat 7:
<jee:jndi-lookup id="MyEndpoint" jndi-name="java:comp/env/MyEndpoint" />
<jaxws:client id="helloClient"
serviceClass="demo.spring.HelloWorld"
address="#{MyEndpoint}" />