I am not totally sure, but I think black purpureomaculatus are only in Singapore and maybe south Malaysia. In Langkawi they are brown, and coast of Kuala Lumpur I remember some individuals found by Konrad Mebert dark but not completely black. But I am not sure
Wow, 4-7 hours flying and in January don´t seems easy. Israel is very very cool. But in northern areas (meditearranean habitats) reptiles are not active and in the Negev also probably they are "sleeping". Maybe can find any species in coastal areas or basking in desert, but I think is a waste of time and money because in april may you can find 100 times more reptiles than in january. I think Dubai has also low activity in january in comparation with march-october
Maybe Senegal is the closer place that you can visit with some hope of finding many species. Northern (Sahel) is bad in winter but probably tropical areas (Casamance, Bandafassi) are good during most part of the year and you can find green mamba (according to Trape is common, but we stayed 3 days and didn´t find it), many Naja species, Toxycodrias, Echis jogeri, etc...