I used these
the short ones stay on really easily, the long ones need either jewelry wire pushed through the arms, or spirit gum to glue them on. I also felt it was important to use some foundation makeup and lacquer spray to make the color match better because the base color is sort of an off yellow silicone flesh tone...
hereThere’s a generic set of elf ears I got off Amazon, they sort of just clip onto the ear! This one came in two sizes but we like drama so I opted for the larger ones. Painted them a little bit with my bronzer to add depth/make them less pale and viola! I have large piercings helping hold them in place too, otherwise I think they would be too top-heavy alone and require a bit of spirit gum or other adhesive....
There are a number of silicone elf ear companies out there. These are nice. Some are a bit pricey for what you get.
If you are looking for the taller type, these are nice with just a little spirit gum and your hair in the right place they do look really good and last a long time (and come in 2 sizes)
If you are looking for a professional level look and have used latex rubber before to blend. These are a bit more, but really well done if you blend liquid latex latex on the edges , . let dry and use a foundation and match the color of your own ears in makeup.
The only thing is , Latex (vs silicone) ears dont last long, They tend to degrade a bit, and last maybe a year before discoloration . But the effect when done right is completely convincing .
Hope that helps. as a side note, the elf ears in the Lord of the rings were made of gelatin and needed just warm water to blend them onto the skin of the ear.