You can find 2 brands of fountain pens at Daiso stores in Singapore — the Platinum Riviere and Daiso’s own house-brand pen. Both cost S$2, have tipped (Western) Medium steel nibs that write relatively well out of the pack and use their own proprietary cartridges.
I think the Daiso pen is better value than the Riviere. It has a larger nib, a molded grip that resembles that on a 1980’s Pelikano, and the barrel has a wider girth. This pen feels more substantial. In addition, the Daiso pen doesn’t dry out while capped but the Riviere does.
The barrel of the Daiso pen has a rubber-like finish, which may not be to everyone’s liking. I’ve no problems with it. Still think it’s great value, and I bought a couple anyway just to practice nib stubbing.