Hi peanut,
at that kinda UK price even if you can find one, try DIYing a seat?
Make yourself a seat pan of the exact shape you want out of corrugated cardboard and masking tape.
Cover it both sides with 2 layers of fiberglass to make a super-rigid laminate.
Note that this is a poorboy copy of how they make airliner cabin floors and they have to survive the impact damage of a fat lady wearing stiletto heels.
Fabricate the appropriate attachments from 16ga sheet steel and bolt them on with big washers to spread the load.
Up to you if you want the foam and cover professionally done or to DIY that too.
Carefully save the stock seat so you can swap back to it if you want to.
at that kinda UK price even if you can find one, try DIYing a seat?
Make yourself a seat pan of the exact shape you want out of corrugated cardboard and masking tape.
Cover it both sides with 2 layers of fiberglass to make a super-rigid laminate.
Note that this is a poorboy copy of how they make airliner cabin floors and they have to survive the impact damage of a fat lady wearing stiletto heels.
Fabricate the appropriate attachments from 16ga sheet steel and bolt them on with big washers to spread the load.
Up to you if you want the foam and cover professionally done or to DIY that too.
Carefully save the stock seat so you can swap back to it if you want to.