"fingerless shooting gloves" in Google gave me a lot of hits. However, most golf gloves will give you good gripping power and are relatively thin. I don't know how they would hold up after having the fingers cut off, unraveling and all.
Two fellas came to H2O a couple of years ago or so selling gloves with the index finger cut out. One of them was a school classmate of my brother, so I bought a pair - I'm also a bit of a sucker for entrepreneurs. They work just fine, but are about the same as a golf glove. I recall thinking "holy mackerel, Kingfish" when they told me the price, after I said I'd take two. I now can't seem to find them online except for an old Facebook account. They are called Proair Marksman gloves.