Single signature P2SH redeem script
First of all, you can use 1-of-1 msig for a redeem script:

OP_1 push(pubkey) OP_1 OP_CHECKMULTISIG


But this one is better:

push(pubkey) OP_CHECKSIG


And of course, you are welcome to use segwit form

OP_0 push(hash160)