GPS is entirely free. What cost money is relaying that information back to you. Since you are talking about GPS I am assuming you want something more than just a beacon style tag. You are looking for something you can insert your own data only SIM card into that you can program yourself to upload it’s coordinates to a website every X seconds or whatever you choose. You also want it to have BLE for the beacon style of the air tag. Self hosting this is not going to be cheap each device would be around $10 a month for the data only SIM.
I have no clue who sells these off the self. You can get an ESP32 with GPS and a SIM card slot. This is basically exactly what you are looking for but you still need to do the programming and manufacture a case depending on the application.
It’s a cool project hopefully with this info you can find an OTS version.
Reading this I can’t tell if you are talking about solidworks or freeCAD. JK but man solidworks is still one of the buggiest programs. If you use solidworks though the Solidworks error report screen is just part of the experience. Still I believe the gold standard for design software out there over NX, AutoCAD, and CATIA.