Firstly
Do you know if your DESFire card is a 4Byte or 7Byte?
Can you provide us with some system information; Photos of readers / card/ fobs etc.
The more you provide the more we can help.
If you are happy to share your card information, this is also what I would recommend
I would recommend a test card bundle or at the least one or both of these
- Mifare Compatible 1K Magic UID – Changeable UID Gen1 (FlexM1-Gen1/XM1)
- Mifare Compatible 1K Magic UID – Changeable UID Gen2 (FlexM1-Gen2)
You will need a NFC capable phone to program the Gen2a or a proxmark3 that will do both the gen1 and gen2
If one of those work, then you could consider a FlexM1 gen1 or gen2a or if the gen1 works you may also consider an xM1
If they fail to work,
You could try the corresponding one of these cards
https://labs.ksec.co.uk/product/mifare-desfire-compatible-uid-modifiable-emulator-card/
If one of those work, then it would still need to be a conversion dngr.us/custom
Amals suggestion above for conversion is actually probably the best option for your situation, the hardest part would be the fact that you would have to be without your card for a period of time if that is possible.
One other option is the FlexMN but lets leave a pin in that one for now 