I can't seem to find anything online or in any dictionary.
My conclusion is that there is no kanji but can anyone confirm this?
Is there an archaic version that has gone out of use?
If we're talking about 一つ、二つ、三つ、etc...
According to jisho.org, "箇" is defined as:
Other forms of this kanji include 個 and 个 as notated on the dictionary entry itself.