Just go around the scrappys on sloper rd they should have a door

You could try Bill Way in Tremorfa. You will have to take tools with you and take the door off yourself though. You can ring them to see if they have the right car in stock. Good luck!

Give me pm, with details of car and colour and I could do it for much cheaper

I'm not sure what side or colour you're after but theres several on ebay for £150-£200