i have a couple of these for my trucks:
https://www.amazon.ca/Uniden-300-Cha...79&sr=8-6&th=1
i also have a couple of handhelds that work great (we use them to listen in on fire/ambulance/forestry mostly. sometimes the airport)
do you know the frequencies you want to monitor? if so, just make sure the scanner you're looking at will pick them up.
does he need it right away or can it wait until black friday/cyber monday - you'll likely save a bunch if you can wait. scanner prices can have big swings - the one i posted above is at almost $184 right now - it will go as low as $115 at times
you can use this webpage to watch for price changes on amazon. it works great!
https://ca.camelcamelcamel.com/
as long as the scanner has half descent reviews it will probably do the job - so no need to break the bank. make sure it comes with a plug-in for the wall unless you have a surplus of AA batteries - ha!