Get a couple of tubeless valves with removable cores, and some wheel milk (I use Just Riding Along).
A few wraps of electrical tape to seal over the spoke nipple holes in your rim, and you are good to go.
I did this with my DT 420SL rims. It seems to be working pretty well. I used Stan's sealant (and Wickes RED electrical tape, because apparently it's faster).
I did a loop of electrical tape offset to one side of the rim, then another loop offest to the other side, finished with a loop around the centre.
I also used some PTFE tape around the base of the valve to help it seal, but not sure if this was necessary or not.