Ken, the best reference I have found on Negrito weapons is by Fox and was published shortly after WWII. I uploaded a couple of PDF files with Fox's research here
Another useful publication that can be found here
online is Negritos of Zambales
, by William Allan Reed published in 1904--the plates are reproduced in reasonable size and those showing Negrito bows I have copied and posted below.
For several reasons, I am doubtful that the bows and arrows that you show are Negrito. The bows are usually very long (and stand much taller than the Negritos themselves). The arrows are also long and usually tipped with iron. And all examples of Negrito arrows that I have seen were fletched with bird feathers.
Hope this helps.