If you have a Sally's Beauty Supply near you, I used to work there, & I know they carry the nail-biting stuff. Although, from what I hear, it isn't as nasty as it should be & most people I know that have tried it end up biting their nails w/ it on!
I would suggest keeping something else around to help w/ your oral fixation.
Like gum or mints or something else you can always chew on!