The refill that does not write, does write, you just have to scrape off the "protective cap". Replacement refills are conventional D1 refills, if you Google them or ask in a stationery shop, they are easy to get. Like here, of course, almost everything has one:

Caran d'Ache D1 refill RNX316 (replacement refill, blue, red, black, 0.50mm)
Faber-Castell ballpoint refill D1 (replacement refill, black, 0.50mm)