Dumping relevant manga pages.
Po-ju - Secret Journey Ch2
Hmm, if you want true growth i.e. it starting to look like a micro-penis - you'd need to put testosterone gel, like andractim, directly on the clitoris. A small amount in the beginning - less than pea-sized. That way, there are less effects on the entire body. You want slight masculinization of the clitoris but not the rest of the body. Andractim is a bit expensive tho cost me about $138 for two tubes. They last a long time 6mos-1year depending on how much you use.
How big you can get it depends on your genetics. Some girls win the gene lottery and are able to get it to 4 inches - then use a pump on it so it can be used for penetration. It's possible to pump it with saline or synthol at this point but it's dangerous (infection possibility) and I don't go that far - you'd have to find a body mod forum and research it cause I don't know the process.
You can get some size from ginkgo biloba since it increases the amount of bloodflow to the genitals. However, it's nowhere near as powerful as straight test on the clit. It's milder and more pleasant.
You can also get a size increase through regular mild pumping, especially when combined with testosterone gel.
You want to do slow pumping, since you want to stretch it slightly and let it heal that way so it will do a little more next time, pumping a lot at once can cause permanent damage to erectile tissue (so no stiff clit). That's pretty much why penis pumps aren't as mainstream as they once were.
and to be clear, pumping is like a 10-20% increase in size per year (and does top out), you need the testosterone to double or triple it.
there was one manga back on gurochan ages ago of a chick getting her clit injected into by some mad scientists that ended up giving her what almost looked like a dick. Would be pretty sweet if someone had a copy of that.
I've actually seen more than one manga with that plot, but I don't have the titles memorized or anything so I can't help you. If you have a page from it saved I think you can do an image search on exhentai and it would come up.
Maybe not quite what you're looking for. But with your description all I could think of is this
(C74) [Rei no Tokoro (Kuroarama Soukai)] Usagi Drops FULL! (Gotcha Force) [English]
>MY SKIN'S CRAWLING
THESE WOUNDS THEY WILL NOT HEAL