The phrase "a thing or so" is correct and usable in written English.
It can be used informally to refer to an unspecified number of items or a small quantity of something.
Example: "I need to pick up a thing or so from the store before dinner."
Alternatives: "a few things" or "some items".
The actor, Boris McGiver, knew a thing or two about woodcutting, so they equipped him with an ax, and he began to chop.
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They know a thing or two about runners so they've included a chest strap that monitors your heart rate.
Big Blue obviously knows a thing or two about enterprise, so it wouldn't be surprising to see it continue to seek an acquisition in the event BlackBerry 10 isn't the panacea RIM hopes it could be.
The Cyrus family knows a thing or two about music, so it only makes sense that another member would soon get involved.
She shows the boys a thing or to, and in so doing, learns that the "hard shell" that earned her the nickname Turtle belies her soft underbelly, which she comes to understand and value by the end of the book.
The PM knows a thing or two about polls, so it was assumed that coming to his decision, he possessed complimentary polls which tended to substantiate his expectations; but then, this is Israel, and matters started to go awry.
Teddy Sheringham knows a thing or two about second strikers, so you are inclined to listen when the Stevenage manager says Kennedy could enter the reckoning for a place in Northern Ireland's Euro 2016 squad this summer.
You might learn a thing or two about the topic so that you can understand their thoughts better.
