Garden shop or farm supply.
I’m not sure if Lowes or Home depot carries them, if they do, it will be a real quick item, they might have them for a week or ten days then they will be gone.
Any potato will eventually start to make eyes, but it’s too late to do that for this year.
Oh, and they are really not a summer crop. They can and do thrive in cooler weather than many other veggies, so it’s best to get them in the ground as soon as possible.
Right now (well, a few minutes ago), I was outside turning over part of my garden.
Tomorrow I will put out lettuce seed, cabbage seed, spinach seed, and carrots. All crops that start very early in the spring and have good yields.
Potato Sprout Inhibitors The purpose of sprout inhibitors is to prevent sprouting in storage. When applied to the potato crop in the field, they also prevent growth of volunteer potatoes in the following rotation crop. Sprout inhibitors function by inhibiting cell division, therefore they should never be applied to seed potatoes and care needs to be taken to avoid drift or movement of sprout inhibitors into areas where seed potatoes are present. Maleic hydrazide and chlorpropham (CIPC) are the compounds most commonly used as sprout inhibitors. Maleic hydrazide is applied to the growing potato crop and is translocated to the developing tubers where it arrests cell division, but does not limit cell expansion. If it is applied too early during tuber development it will limit tuber size and yield. Chlorpropham is applied to potatoes in storage. It is a potent inhibitor of cell division and should not be applied until after wound healing.
Some seed houses either carry them too or sometimes they dropship them from specialist growers. They run about $1.80 per pound plus shipping. Your local garden supply or hardware store (Ace Hardware here does) should carry them over the next couple of months - but don't wait they will be gone fast, and they don't reorder them.