You can't make an item to counter silence in general, it breaks way more than it fixes. You can't nerf kass without breaking him on SR. What you can do, is introduce some anti-kite dominion item that would also help against other hard to counter champions like Nidalee.
Randuin helps counter ranged ADC kiting on SR. We need a MR version that counter-slows any single target spell. It wouldn't completely shut down kass, he can still jump in and combo, but he can't fully capitalize on his slow to get far enough away to wait for ult cooldown and escape, since he is also slowed, and as soon as that silence lets up he is going to be counter CC'd. He also takes a large risk attacking a grouped team, since he would end up slowed in the middle of them.
Summary: MR version of Randuin, possibly as a rework of odyn's veil: When hit by a single target ability, slows the attacker's movement speed by [insert balanced number here]% for [other balanced number] seconds. Possibly add a movement slow to odyn's active.