I just scraped my wall with a chair, so I added paint to my weekly shopping list as a ______ purchase.
The other day I went to close up a bag of bread, and realized I was out of clothes pins, so I add a _______ purchase to my shopping list.
I checked my shopping list for ________ items, and remembered that I wanted to get cookies for a snack later.
Some purchases happen on a scheduled, repeating basis -- e.g. weekly grocery shopping.
Other purchases happen on an irregular basis. They might be one time purchases (e.g. a socket wrench) or purchases that will repeat, but not in a scheduled way (e.g. command hooks, which will be purchased again at an indefinite time, such as next time you need to hang something up). They might be purchases which are motivated by an unexpected external need, or they might be motivated by whim of the purchaser (I feel like buying muffins today).
I am searching for an adjective to describe this second category of purchase.
Here are some words that are close, but which I feel do not capture the meaning I am attempting to convey:
One-time - the purchase might repeat, and even disregarding that, I feel that the category is not defined by whether or not the purchase repeats, but by the regularity of that repetition
Irregular - to me, this fails to capture the element of discretionary-ness and choice
Sporadic - again, I feel that this fails to capture the purposefulness that might be present, and instead implies a level of external chaos (like, if purchases just appear on your shopping list at random). I also perceive a connotation of scarcity in the term "sporadic", which does not necessarily apply to the category I am envisioning
You may disagree that one of the above words is not adequate. But if anyone's got further suggestions, I would, of course, appreciate the input.