You don't need to be an 'investor' to invest in Singletrack: 6 days left: 95% of target - Find out more
Ideally sub £40 odd give or take.
Not something that pairs to a phone.
Ability to remove or reset codes would be great.
If it can also be run while moving that's possibly useful.
Moon on a stick possibly. Tried to Google but it seems to me Google is not what it used to be and has become a hotline to videos made by people who know less than I do , or take you to a sponsored site that a bot has pulled information together and tries to sell you things that won't do what you want, isn't made anymore , costs 10x your budget...
Depending on what exactly you need, I put an Ali Express special in our base-spec transporter so I could see the coolant temperature and fuel economy. Plugs in and gives you real time access to all the engine data available in your vehicle and displays it on customisable gauges/graphs. And of course it reads & clears DTCs. £35 delivered.
https://a.aliexpress.com/_EynrUnB
Depends what you want it to do. I have an Autel ml629 handheld unit, was about £120 ((seems to be around £70-£80 now), but it does diagnose airbag and abs issues, which many don't do. Saved me some big bills.
+1 for Autel