Options that could go here:
- Hammer Arm - Good coverage and also reduces Rhyperior's speed, which is good for Trick Room and stuff
- Poison Jab - Coverage against Fairies and also slower grass types, also good neutral coverage
- Megahorn - Although not the best option, it has very high base power and can hit many things neutrally for a lot of damage. Also hits the occasional psychic types like Slowbro and Cresselia very hard.
- Rock Polish: A set-up move for Rhyperior, which remedies it's low speed stat and helps it pull off a sweep.
All in all, any of these works, so it's upto your team as to which coverage move you choose. If you're team already has good coverage, go for Rock Polish.
Hope I helped!