Bonus repayment in subsequent year Deloitte

My signon bonus was 5000$ . I received 2500$ a week before i joined in 2019. For the remaining 2500$ , i received it along with my first pay check . My first regular pay was 1325$. I received my first payslip with the remaining bonus . My first payslip says 

Total earnings 6325$( including bonus)

total taxes 1718$.  

Net pay received as per first pay slip 2108$

 

Now i quit my company in jan 2020. So i had to repay the bonus 5000$ , including taxes.

I encashed my leaves for 2525$ and i deposited 2475$ electronically 

2475+2525 totalling 5000.

I received medicare and fica returns from my employer 3 months later for 270$.

 

Now my 2020 w2 says my total earnings in 2020 was 9000$ which includes my leave encashment of 3200$ before tax.

 

How do I claim the tax i paid for my bonus which i didnt earn ultimately.

Employer says they won't issue a corrected w2. I don't have the 5000$ reduction in income in the w2 as well.

 

Please advise how to proceed in this situation.

Met multiple tax consultants and no one gave a proper answer.