I have never seen a needle clamp. One major American engine mfgr. (that is still very much in business) use to apply a tiny bit of blue loctite to the needle threads of their carbs. When cured, the needles were turned to break the lock loose and the loctite just served to tighten the threads a bit and resist free turning. This was applied well up on the threads well away from the needle end so that no residue could foul the carb jets. I'm not recommending this but just stating what I have seen done in the past. I don't know if this company is still doing this or not because I haven't bought one of their engines in a few years.
A greater issue might be the vibration you speak of! Severe vibration over time will do damage to the airframe and engine. Have you checked the prop and spinner balance? Prop shaft running true? Weak firewall or mounts? Testing the engine on an airframe with the wings removed can also exhibit high vibration. Over time, vibration can also damage the plug cap making it hard to keep in place and the silicone insulator inside can break down creating an engine miss or worse. What size prop are you running? A too small prop running above a normal RPM can also cause excessive vibration.