| When you say "fake", do you mean one of the Chinese fakes that is branded as the real thing, as opposed to something like a Vintage?
I bought a Chinese fake Les Paul guitar from Samin.cn, one of the biggest suppliers of rip-off Gibsons and Fenders. The tuners and indeed other hardware on it were pretty poor and I ended up replacing the lot.
You don't say what happened to the tuner you need to replace - did the shaft snap or a thread strip? If your bass has iffy tuners, your best bet would be to replace the lot with decent ones off eBay.
Adrian | 
