HEY! Check online or locally if you have the store nearby .... but when I want abalone shell pieces I go to Jo-Ann's Fabrics and Crafts supplies.
I bought several of their 12-oz bags to take home and play with ... they weren't more than about 7 or 8 bucks. (oops, i guess they are sold in 24oz and 32oz sizes, lol...)
Side note, however ... the WHITE is perfectly good natural stuff. The blue, black and other colors, while they LOOK nice at first, are dyed. Wash them VERY WELL to ensure no excess product is going to spread throughout your acrylic when you cast or glue.
DO NOT ATTEMPT TO TURN THIS PRODUCT NORMALLY. The material is a form of calcium phosphate (bone) that can chip and shatter and break loose from the matrix material you have them cast or glued into. SAND THEM DOWN FROM START TO FINISH AND USE VERY GOOD AIR FILTRATION AND VACUUM TO KEEP THE DUST DOWN. The use of a FULL FACEMASK is highly recommended if you like your eyes the way they are, even if you sand it down!
Oh, here it is online ...
https://www.joann.com/large-polished-crushed-shells-24oz/14158273.html