Best filters for the DJI MINI 4 pro

Hi guys, this is my first post, I’m looking for a bit of advice. I’ve got the mini 4 pro and I’m looking for the best filters for it, some say the freewell filters, also the best price, don’t mind 2nd hand as long as they are not damaged. I am a military veteran and I do have the BlueLightCard + Veterans discount card if you know any shops that sell them and recognise the cards that would be great, Thanks in advance Terry