The critical concern here is then which category you satisfy. In the case you're going through employer dependent category, you have to obtain employer sponsorship (agreement and commitment) to meet USCIS's requirement even if you do everything and pay all the money yourself.
However, in this case, contrary to common misunderstanding, you don't need to switch to the job listed on your labor certification and I-140 petition, until your I-485 is approved. In other words, if you could find an employer who contracts you a position available upon your I-485 approval, you can use that position right now to apply for LC without changing your current job.