I have used keysinthepost.com - if i am feeling particularly distrusting or suspicious i get it delivered to a friend / family members address where the car never is - They even suggest this on the site.
However the issue is programming... On one of my cars programming was as simple as turning the key to the II position 10 time and then clicking the button on the key.
Other cars need to be plugged in.
I have also bought fobs from scrappies and then just got a new blade cut. But the programming situation still exists.
I'm tight, and I also lose keys... On my previous car i did away with the clicky fob thing and just used it in the door like a regular key, you then got 10 seconds to put the key in the ignition before the alarm went off.... This caused rage in my missus but it seemed acceptable to me for 4-5 years.
My current car came with one key, apparently the key is quite rare, there was a fire in the factory making them shortly after the production of the car started so they changed fobs (from 4 button to 3 button) new keys/fobs are north of £300 due to the scarcity.
The fob fell apart recently and the thought of spending £300 made me ill, so I bought a new casing from Temu for £7 and swapped over the internals including the RFID thingy chip). To my amazement the new fob feels better than he original as does £7 vs £300
I have also had a spare blade cut just in case i need to get into the car in an emergency - but the blade alone wont start the car.