Teton, AnEv makes extremely helpful points. Now that you know what's kind of going on here, fix that baby, or even see if there's a replacement jack at an RV used parts (dealer, junkyard, etc.) nearby. The weight of these things will kill a good deal on shipping - me thinks.
Also, not sure yet I want to split up my Reico set of four. My HiJacker set of three is another matter all together. And I'm not coming your way anytime soon anyway.
Post some more pictures here for the guys if the fix doesn't make sense, they have some excellent, long-term experience and assistance waiting for you.
I looked at my Reicos yesterday and found mine doesn't have the slot. It's a hole, both sides. If you examine your slot and it appears "manufacturer intended" just re-position the head and tighten it up like AnEv says. If it appears the slot was torn, turn the tube like he says.
If still confused, get more questions and pics posted, they'll guide you right. Ref your PM, I don't have time right now, and when it comes to your particular issue, I'm not the best choice anyway. Good Luck!