Given Michael’s reminder, and Bo’sun’s suggestion….
Yes, there is a company called Base Camp that specialises in paraffin-lamp etc. spares:
base-camp.co.uk
https://www.base-camp.co.uk
I have just looked them up to verify this. I have used it too, to refurbish a “Vapalux” lamp – though the result was a slightly disappointing because modern mantles give a distinctly yellow rather than bright white light.
So if need spares, try this company!