What constitutes a deal for you these days? Last time I got slugs for anywhere close to $1/rnd was a business closing up. Buckshot can be hard to find in general with prices on some stuff up to $3-5/rnd.
Friend has been looking for a while as well. He finally caved in and bought Sellier and Bellot 3/4 oz 2 3/4 inch rifled slug $290 for 200 rounds.
https://g4cgunstore.com/product/sellier-bellot-20-gauge-3-4oz-2-3-4-inch-rifled-slug-5rds-2/
Cabelas has them for $21 for 15 winchester if you want to deal with them.