Split developers usually have a solution A which contains all of the developing agents, and a solution B which is a basic solution, Kodalk (Sodium Metaborate), Sodium Carbonate, borax, lye, combinations of the above are likely suspects. A solution of 5g Sodium Carbonate in 1 liter of water is an easy place to start. Maybe some sulfite also.
The idea idea is that the process is relatively unaffected by time. maybe 3 minutes in A then directly into B for another 3 minutes or so. I've done some reading on divided developers but have never tried one, so I may be less than 100% correct here.