The League Two side are desperate for firepower and have lodged bids for Crewe forward Zola and Burton Albion man Harrad.
Cardoza told the Northampton Chronicle & Echo: "We won't be gazumped on either player.
"If anything happens to stop either deal happening it will be because the player in question has had a change of mind.
"I don't believe we'll be outbid in terms of wages or a fee. I think I've done it on the basis that we won't get outbid."
Source: PA
Source: PA