Catalyst Game Labs is now selling PDF copies of the Experimental Technical Readout: The Clans supplement for BattleTech.
From their website:
Experimental Technical Readout: The Clans samples a number of new designs being produced by the various Clan powers who now call the Inner Sphere home. Infusing a new wave of advanced Clan technology into the older models at their disposal, most of the designs featured in this book incorporate a mix of modern technologies and design standards the likes of which the Inner Sphere has yet to face in open battle. Statistics and Record Sheets are included for 13 new experimental BattleMechs, ProtoMechs, vehicles, aerospace fighters, and battle armor are presented in this book, ready for play in advanced BattleTech games.