When it comes to a female C99 supplier you really have limited options. The best bet is Female Seeds which are stocked by most seed banks or you can buy direct from them. Brothers Grim (original breeder) has re-released this strain but most grow reports have come back saying that they are not the same as tthe original so it would appear that the re-lease was a bit of a cash grab.
There are a few other female C99’s on offer but most of them not legit. You can check out the lineage on most of them on seedfinder.eu
Female Seeds is basically a cross of 2 x original C99’s, the grapefruit pheno & the pineapple pheno which were the main 2 & most popular pheno's. It’s probably your best chance to find something decent.
Either way you are looking at a pheno hunt if you want to find anything close to the original. I've done one so far & it was ok but more of a 50/50 Indica/Sativa where as thee famed C99 was meant to be a more racey Sativa dom. I will get round to working through the rest of the pack sooner or later but don't expect to pop one seed & find the grail, not unless you are lucky as ***k.