there are thimbles on the market designed especially for this. The one I tried is a Dritz Adjustable Thimble.
It didn't work for me because it was too small. Not flexible enough to fit over my finger. I have to figure out a way to stretch it. since you use a small thimble anyway, they should work well for you. Quite inexpensive. i posted a link you can use to either shop for one online or to at least see what it looks like.
http://www.amazon.com/Dritz-Adjustable-Plastic-Thimble/dp/B000FKGUFO
There are at least two other types on the market. One would be too big for you. The other looked dangerous to me. No protection against the needle slipping and stabbing you under the fingernail. Ouch!!!
google on "thimbles for long fingernails" to see if there are more.