Limit some products to be purchased individually

I have a case where I need to sell some products individually, they can't be added to cart with other items....
in other words, items selected can only be sold by it itself, the order would only have 1 model (not quantity limitation, model limitation on cart)
is there a module or customization for this?

Restrict Checkout can do this. You could set up a restriction like this, which would disable the checkout when the cart contains both a specific product, and some other product:

------------------------------------------------------------------------------
RESTRICTION #1
Name: Disable checkout when purchasing Product A + other products
Message: You must purchase Product A by itself
Rule: Product is Product A
Rule: Product is not Product A
------------------------------------------------------------------------------

Feel free to take a look at the screenshots and demo site, and if you're interested let me know at www.getclearthinking.com/contact if you have any further questions.