Withholding tax from ESPP

Hi, and thank you for any help in advance. Apologies this may have been asked before, I tried looking for recent and exact scenarios but wasn’t successful.

I don’t live in the US, never did. Was not born there. Have no green card or residency status. Have only been there a few times for vacation. I work for an American company. So I think I fall under the non-resident alien category.

In December 2024, I sold some ESPP company shares I had and unfortunately got charged withholding tax because there was an issue with my W8BEN form. I am trying to get this tax back. I like in a country with no capital gains tax.

I tried to lodge a tax return myself on the IRS website however it seems like I am not allowed to as I am a non-resident alien and MUST use a tax accountant, is that correct? After googling, I have also now prepped the following forms for the return: 1040-NR, 1042-S and 1099-B.

Have I missed anything and is looking for a tax agent to file my returns the only step left? If yes, any recommendations for a cheap and reputable tax agent that can help with this which I believe is probably a simple case?

Thanks in advance!!