Smoke & CO Detectors - Where to buy bulk?

Hey BP,

Upgrading smoke and CO detectors across two buildings, six units. In need of ~15 smoke detectors and nearly as many CO detectors to meet the village code. Unable to install hardwired so looking at 10 year battery models.

I’ve browsed Amazon and Home Depot and - while there are many options, the pricing is just mind boggling. Looking at upwards of a grand+ for these retail.

Any suggestions on where to purchase bulk detectors would be much appreciated. Hoping someone has the intel.

Thanks!