I pronounce it like somewhere between "boys" and "buys" but I'm not really sure if this is right.
As for the Japanese names it's not just sports announcing. In my (very limited) dealings with Japanese people they always put the stress on the first syllable of the name.
Interesting discuss
I pronounce "Buijs" like the Dutch pronunciation of Google Translate.
Japanese language pronunciation mostly based on Gojūon(aka fifty sounds). wiki
Each kana corresponds to one sound (ex: a, i, u, e, o, ka, ki, ku, ke, ko ... etc)
The case above, it should be SA(low) KU(high) RA(high) and KI(low) MU(high) RA(high).
Btw, R in Japanese sounds like L in English for me