OP_SIZE <60 - n > OP_EQUALVERIFY < pubkey > OP_CHECKSIGVERIFY
Instead of OP_EQUALVERIFY, OP_LESSTHAN OP_VERIFY can be used. Then, smaller signatures are also accepted. Also, OP_CHECKSEQUENCEVERIFY or OP_CHECKLOCKTIMEVERIFY can provide an incentive, to produce the smallest signature in a given time, and then, broadcast a valid transaction earlier, than other competing miners.