It's time to call-up Neftali Soto IMO. The Reds play 6 games in AL parks and need a DH. The team needs some RH Pop. Votto needs rest and could DH while a Soto/Hannahan tandem shares 1B for a week. Soto is up to .291/.327/.453/.781 with 9 HR in 258 Abs. Against LHP he sits at .312/.361/.623/.985 with 6 HR in 77 ABs. Here is the missing lefty killer the team needs. He doesn't walk much, but he's got pop and has been playing some 3B as well to add a little positional value. Over his last 10 games .400/.415/.675/1.090 in 40 ABs.
Given his positions, he may not be the best use of a bench spot all season, but over the next 6 games with the DH involved, his current hot streak and his ability against LHP, he'd be really darned useful IMO.