The only thing I know of that "works" are penile implants. These can be used to create more length and girth- but I think they can interfere with sensitivity. You would need to talk to a surgeon, since there are probably advances in this field that I have not kept up with. There are different types, the one I am most familiar with is a pump that is usually used when erectile failure is involved. I do know, however, that some implants have been used for cosmetic reasons- to look bigger. Go to a credible doctor at a University based hospital or some other prestigious hospital to make sure you don't get involved with anyone disreputable who could harm you.
nothing i know of except surgery. incidentally, i wonder if your penis is as small as you think it is. i have noticed some men think they are really small when they are in fact average, and have based their standard of comparison on porno movies. remember, the camera makes everything look bigger, not to mention those guys are larger than average in the first place.