Wayne, I use Lithium Chloropalladite routinely for my Pt/Pd prints. Along with Cesium and Ammonium Chlorpalladite.
Someone else will have to answer the question about subing K Chloroplatinite for Na2, just don't know. For some reason, my gut says it will not behave the same as Na2, but it's been wrong before.
Here is a good thread related to this question