Maybe you already find an answer, anyway I'll post it.
WCS InfoCenter describes the steps to follow in order to integrate the admin UI files in the solr-search web app:
http://www-01.ibm.com/support/knowledgecenter/SSZLC2_7.0.0/com.ibm.commerce.developer.doc/concepts/csdsearchperf.htm?lang=en
However it has few errors also reported in the IC page's comments. So I'll describe the steps here, valid for FEP7 Toolkit version:
1) Download the SOLR version 4.3.0 from: http://archive.apache.org/dist/lucene/solr/4.3.0/
2) Unzip solr-4.3.0.zip
3) Copy the following directories and files from the unzip folder into the Search-Solr/WebContent directory:
css
img
js
tpl
admin.html
favicon.ico
4) Open the Search-Solr\WebContent\WEB-INF\ibm-web-ext.xml file for editing.
5) Find the enable-file-serving flag and set it to true.
For example, in bold:
<web-ext
xmlns="http://websphere.ibm.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://websphere.ibm.com/xml/ns/javaee http://websphere.ibm.com/xml/ns/javaee/ibm-web-ext_1_0.xsd"
version="1.0">
<reload-interval value="3"/>
<context-root uri="/solr" />
<enable-directory-browsing value="false"/>
<enable-file-serving value="true"/>
<enable-reloading value="false"/>
<enable-serving-servlets-by-class-name value="false" />
</web-ext>
6) Save your changes and close the file.
7) Deploy the Search-Solr project; Right-click the project and select Java EE > Prepare for Deployment.
8) Update the following files:
Search-Solr\WebContent\WEB-INF\web.xml
9) Change the URL pattern for the SolrSearchServlet servlet to /Search-Solr.
For example:
<servlet-mapping>
<servlet-name>SolrSearchServlet</servlet-name>
<url-pattern>/Search-Solr</url-pattern>
</servlet-mapping>
10) Save your changes and close the files.
11) Publish the search EAR.
hope you can find it useful.
good luck
Francesco