Ive been having issues at one of my sites where wardens are not reporting their areas clear during drills. Im possibly looking at introducing a paddle system (last out picks up the paddle and reports the area clear). Can anyone advise on where to buy such a product

How does he/she know that he/she is the last one?

Surely there is a risk of an area being declared 'free' when a Warden [and others] are still in it?

Retrain or replace the Wardens.

Your associating one action (picking up the paddle), with the assumption the building is now clear (last one out), but have missed out the sweep of the area.

Nominate wardens/deputies to do the sweep, and report. If they are not doing the sweep, then get another warden. A paddle adds little value, and the potential for a lot of confusion.
The only way I can see a paddle system working is by having sets - 1)in the office, 2) in the toilet, 3) in the meeting room, etc, each warden is then to present their "full set" to demonstrate that they have checked the office/toilet/meeting room etc.

I don't really understand the problem to be honest.

But if you wish to use a tally type concept, it would be sensible to make you own system, even utilising a local printing firm to knock up the tallies.

However, if you have money to burn, you could buy something like this
http://tagevac.com/about-us/what-is-tagevac/