TNZ nursery has a few listed. Here is a link that might be useful: TNZ Nursery

Yaupon is borderline in upper zone 7. Some cold years it can freeze back. I do not believe it is native to Long Island, but I could be wrong. Goodness, for zone 7 there are SO very many hollies that are better looking than American Holly. Fosters #2 is nice, fast, good berries. Smaller leafed. Nellie Stevens is the default holly planted here. Takes shearing very well, but does get TALL. Look into 'Mary Nell'. Incredible leaf gloss and BERRIES, oh so many berries most years. 'Blue Maid' is a nice very hardy blue holly which grows slowly to 12 feet. It takes its time and will not need much pruning. Castle Wall is a very upright grower. (another Blue Holly). Chindo Viburnum might be worth looking into, if it's hardy in your area. Fast grower, very glossy, no spines. This post was edited by dave_in_nova on Mon, Sep 16, 13 at 9:43

My goodness. I might have to buy a Nellie Stevens and carry it next to mine to see the differences. So far my best moment identifying plants was with Fraxinus family ash trees. The "U" shaped bud of the Fraxinus Americana white ash helped me out. Anything similar I should be looking for? The foliage is too variable. My two identical Holly of some kind trees both bloomed lightly last year. Neither has ever had a berry. Bloom time this year is soo early. Of course March was the warmest in 130 year of record keeping. heard it would have been a top ten warm April! My plan is to hunt down dwarf/small varieties of both Ilex opaca and Ilex cornuta and hope I get lucky.

Interesting. So I have been watching the fruity one for 3 years now, and it seems to have that yellowish tinge every year. I just thought it was its natural color. It does seem to have a lighter colored leaf even in summer. Below are some pix I've taken at different times of year. (Yes, I'm obsessed with the stupid tree :-). We did have a dry late summer, maybe that contributed. But on the other hand - look at the foliage color difference between the two hollies even in summer: 2016-11-12: 2017-01-12: 2017-08-16: 2019-05-22