Are Heavy Kettlebell Swings Better Than Deadlifts?]
This is an excellent article on why you need to swing a heavy Kettlebells.
The information extrapolated in the article indicates that load of 50% to 100% or your body weight need to be used to elicit the optimal training effect.
That means if you weight 200 lbs you need to swing a 100 to 200 lb Kettlebell.
As you mention, there are some handles you can get that attach to a heavy dumbbell that will work.
However, another option presented in the article is the…
Hungarian Core Blaster
About $20.00 worth of pipe form Lowes and some Standard 1 inch Weight Plates work.
I’ve loaded my Hungarian Core Blaster up with 175 lbs for “Kettlebell Hungarian Core Blaster Swings”.
The Hungarian Core Blaster allows you to increase or decrease the load, as you like. It is a very effective training tool.