What size of toilet is used in Philippines?

A friend of mine is a business woman living in the Philippines.  She is not "rich" (not even by Philippine standards) but she does own her own small house.  She loves the bidet I have installed in my apartment, which is just an accessory that bolts onto the top of my toilet.  So, I thought of ordering a similar one off of Lazada (kind of like Amazon in the Philippines) to have it delivered as a Christmas present.  But there are two different sizes, 1/2" and 7/8" (15/16), which correspond to the size of the water connection on the toilet tank.  I can't ask her what size to order, as that would kind of spoil the surprise.  (!)  And they do sell adapters to go from one size to the other, but the adapters are terribly expensive...at least half the cost of the bidet.  So I need to get the size right when I place the order.  I tried googling, but couldn't find the results I was looking for.  Not knowing that much about plumbing, maybe I just didn't use the right search words?