There is the Redskins "Rarities" bootleg album, but this is only available on vinyl and not CD.
There are a few compilation CD's that feature tracks not available on "Neither Washington Nor Moscow". These are -
"Wake Up" - Levi Stubbs' Tears (live from the Redskins last ever gig) "Best Of Peel Sessions Par Bernard Lenoir" - Unionize (Peel session) "Winters Of Discontent" - Kick Over The Statues (Peel Session) "Abstract Records Punk Collection" - Lean On Me (single version) & Unionize "They Shall Not Pass" - Lean On Me (single version) & Unionize.
The "Wake Up" CD is still available from the wake up website (see links section). You should also be able to pick up the "Abstract Records Punk Collection" from amazon. I think the other CD's are all deleted now, but you might be able to pick them up off ebay.
Hopefully Cherry Red Records will be reissuing the Redskins album and including some bonus tracks which have never been released on CD before. They are currently waiting to hear back off London Records to see if they can licence the album.