From Prolewiki:

In contrast with the high bourgeoisie or ‘big’ bourgeoisie, most petite bourgeoisie’s means of subsistence are not entirely derived from the exploitation of the labour of others.

I haven’t heard of “working class petite bourgeoisie” before, and I don’t think it’s a necessary distinction. The petit bourgeoisie class already includes those who derive some of their income from exploitation and some from their own labour.

A small business owner is in the same position; they own their means of production and can thusly exploit others for their labour, but they themselves also have to labour in order to keep their business going. Yet these small business owners are by no means working class, even in part.