Thanks OldMM. I'll check to see what my local upholstery shops have in stock. And thanks Marsal for the breakdown of the different trims available. If I strike out at the upholstery shops, JC Whitney is next. 

There were a few different ones over the years apart from the rare as rocking horse poop stainless 3 piece early cars. It depends what year your Mini is and what you are wanting to achieve, of course any of them can be cut to length and used between the flares if you have that set up.
1. Plastic smooth chrome full length. GFZ107.
2. Fluted plastic chrome full length. GZF105A.
3. Black rubber textured used on later Mini's along the sill between the flares. Not shown.
4. Smooth black fluted plastic usually used between the flares (maybe aftermarket). GFZ108.
The pictures are not very clear so before ordering i would talk to someone to make sure you are getting what you want.
I have got the black textured from JC Witney before but it has been a while.
I have also seen the door edge guard used which is available in black or silver from your local parts store in 20 foot rolls but it is a little narrow but also far easier to install as long as you don't have over sills installed (too thick).

I buy mine from a local upholstery/trim shop, it has small metal clips inside that makes it hang on-

I pay $2.00 a foot, usually buy 10 feet, cash,no tax and there goes another $20.00

Big AL

I'm looking to replace the trim piece that fits over the door sill seam. The trim I'm replacing looks to be made of a shinny vinyl material [GFZ108]. I seem to recall seeing a much thicker rubber trim piece with a ribbed texture. Our host refers to the trim I have as "non-fluted" implying that there is a fluted variety. Perhaps that's what I'm looking for. Can't seem to find it. Any ideas?