Check out this T3 Dock: OWC T3 Dock ...Might be a possibility. Yes, this T3 Dock is pricey, but it has other ports that might be effective for your use. ...Just a thought.
BTW, Apple didn't fail to engineer a one-step adapter for you. ...When Apple pushes technology by deleting old technology, particularly like FW800 which was not as widely used as USB 2.0, Apple always lets 3rd party manufacturers make the transitional adapters. It's tough when one's on the short end of that stick (I also used FW800 drives for my backups); but, one must simply accept the transition, get the gear needed to continue one's use strategy, and get on with it.