Xiamen has too large of a population and Khabarovsk may be too small
That is what I thought, but populstat says Xiamen had 114,000 in 1910, while it had about 96,000 in 1890. Wikipedia says the city had 300,000 people, with only a few hundred foreigners, by 1911. I think the city fits the criteria of being less than 300,000, especially with only a 15 mile radius.
Laoag had 37,000 but as it will be transported with a populated portion of its province, the population might go over 100,000.
Khabarovsk had a population of 40,000. There are some nearby villages, but probably not enough to reach 50,000.
Bien Hoa will be my replacement claim for either of the two you think might not be suitable. Alone it had a population of 19,000, however, within its perimeter, it includes a portion of Saigon and several villages, which totals around 100,000.