I found one with a quick Google but it wouldnt let me get onto Quakenet.
If you find one you will need it to connect to the following:
I might try and setup a Java based IRC client somewhere sometime. Only problem is I cant test it out on Longhorn as I've no Java support at the moment.
You could try going through a proxy server. I kow DCU has one but I'm not sure if you can run IRC through it. Lads on Rez were having a problem with that last year. Though I think they fixed it going through the Redbrick server or getting a trust or somesort.