I got one from Harbor Freight but can't beat that $12.50 on amazon.
Don;t get too spendy and break the budget on this item if you're just serving beer. It's good for many things but don;t waste your time trying to read the mash!
I use mine mainly for checking AC vents and other surface temps like skillets and sauce pans these days.
When checking beer in the glass temp I whip out the trusty superfast thermapen
, and have an accurate reading in seconds. This device I use for everything