The seller has agreed to cover the cost of some repairs. The closing attorney charges a fee to put it in escrow, would I be able to ask for a cashier's check from the seller?
Normally the way seller concessions work is that it’s just a dollar amount from the seller to the buyer at closing.
Whatever the buyer does with it after closing no one cares about. No need for escrow.
If this is a concession, then it should be a credit at settlement and there would be no need for escrow as @Mike McCarthy indicated. However, if your contract states that the seller has agreed to escrow $x for repairs for which the total $ is uncertain... then you'll need that escrow. I would make sure the escrow is large enough to cover any conceivable repair bill otherwise if the escrow is short your seller will go dark.