I personally own the Maverick ET-733 but it is a lot money for what it is (over £50) but it does all I need it to do and easy to programme and is more accurate on temperatures, than the inbuilt probe on my ProQ.
Some of the ThermoPro models £25-£35 on
Amazon (depending on the model) seem well reviewed by customers who have bought it off there, which is always a good guide to the quality of a product I find.
I prefer wireless receiver thermometers as you can just put the probes through the probe holes on your smoker and if you trust the remote/receiver then you can sit in the lounge, go back to bed or go about your daily business and just listen out for the alarm if the temperature drops etc. Without keep going out to check on it manually.
You can even get some remote probes that pair up to your iphone/android via bluetooth now, using an app, but the reviews have been very indifferent on them from what I have read so far.
You can buy manual ones for the meat only for well under a £10, but you have to keep lifting the lid to check it, and as the internal heat from the charcoal, seems to be of more concern to you then a remote one may be better? that keeps an eye on both the meat and the internal temp of your smoker.
p.s. The probes on my Maverick are 6ft (they sell longer ones) but 6ft is the minimum length I would want on a probe personally just so I can position the remote on a table/chair a distance away from the actual smoker. Although you can attach the remote directly to the smoker if you wish, with some models.